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The S.G.C. is invaded by an alien life force that takes up residence in the base computer system – and in Major Carter.

FAN RATING - 6.38 
DVD DISC: Season 4, Disc 5
WRITTEN BY: Peter DeLuise
GUEST STARS: Gary Jones (Technician), Teryl Rothery (Dr. Janet Fraiser), Dan Shea (Sgt. Siler)
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The S.G.C. makes contact with a world whose address was taken from the Ancients' repository of knowledge ("The Fifth Race"), and sends through a M.A.L.P. probe. The video transmitted back to Earth reveal a highly developed society. But a bolt of energy strikes the probe, and it begins to levitate and fly through the air. The video signal terminates, though the S.G.C. computers continue to receive a tremendous amount of data back through the wormhole.

Carter and Technician Davis [Harriman] cannot shut down the Stargate, so Jack O'Neill rushes to the Gate Room and throws the emergency disconnect switch. The gate shuts down, and the rest of the base power goes with it.

Emergency power systems kick in, and an examination of the computer systems shows that the alien world transmitted some sort of virus through to attack their systems, piggy backing it on the M.A.L.P. signal. The dialing computer and all redundant systems, including the iris, are inoperative. Major Carter recommends reformatting the system to eliminate any trace of the alien computer virus. Meanwhile, the base is put under quarantine.

But the team soon learns that this is no ordinary virus. It is highly intelligent and highly adaptable – possibly even a living entity, a digital consciousness. The entity uses spare M.A.L.P.s in a storage room to construct a make-shift mainframe for itself. It hides out there while Carter and the others are reformatting the computer systems.

When the entity comes out of hiding, it attempts to communicate with them. O'Neill encourages General Hammond to destroy the make-shift computer system that the entity has built; but Daniel Jackson and Major Carter suggest trying communicating with it. It has even provided an interface for them, complete with monitor and keyboard.

Hammond grants their request, and Carter is selected by the being to interface with it. But it has no desire to communicate. The system is a trap, and the entity uses a powerful electrical pulse sent through the keyboard to transfer itself into Sam's mind. Back in the infirmary, an E.E.G. scan of her brain reveals that her own consciousness is subverted, and barely present. The entity is in control of her now. It cannot speak, but it does communicate with them when they provide it with a computer voice synthesizer.

The entity explains that the M.A.L.P.'s radio waves, though benign to humans, did a tremendous amount of damage to the alien world. The entity was sent back as a weapon to destroy the attackers, but it failed in its mission when Hammond ordered the Stargate shut down. The entity took control of Carter in order to survive, because it saw how important she was to the base, and knew that they would not kill her to eradicate the entity.

Hammond and O'Neill recognize that they may not be able to get Carter back, and may have to make the hard choice to terminate the entity. But they allow Daniel to speak to it first. He tells the entity that it was not an attack, but a misunderstanding, and that they will never send another probe to its world. But Jack is fed up with the entity being in control of the situation, and takes over. He threatens to send dozens of probes through to the alien world, to destroy the entity's civilization. It is horrified at the prospect, and finally chooses its world over itself. Jack demands that it leave Carter's body immediately.

The being stands up and exits the infirmary, and is quickly cornered in the corridor outside. It raises Carter's arms upward, and electrical pulses stream out of it and into the base systems. O'Neill shoots it with a zat gun, but it seems to have little effect. He hesitates, and shoots it again. Sam falls to the floor, unconscious. Two shots from a zat gun kill.

Sam's body is rushed back to the infirmary, where she is put on life support. Dr. Janet Fraiser reports that there is no trace of the alien consciousness in Carter's mind – but there is no trace of Sam's, either. She is essentially a vegetable, her body kept alive by a ventilator.

Colonel O'Neill sits at her side and ponders how long to watch her like this before ending it. Meanwhile, Sergeant Siler is preparing to destroy the entity's computer mainframe in the M.A.L.P. room. He calls for SG-1, suspecting that the entity has found its way back.

When O'Neill, Teal'c, and Jackson arrive, they find the message "I am here" being repeated across the computer screen. Believing it to be the entity, O'Neill prepares to destroy it. But Jackson believes it is Sam – the entity, after all, said it could not return to the mainframe because it had outgrown it. It knew that the only way for it to save its world was to die, so it transferred Carter's consciousness to the mainframe before O'Neill shot her.

Dr. Fraiser confirms that the pattern matches Sam's E.E.G. readings, and manages to provide a conduit through which Sam's mind may be returned to her body. The alien entity has been destroyed, and Sam is restored.


  • The team speculates upon dialing in to the alien world that it may have once been inhabited by the Ancients, the race of aliens who built the Stargate system but moved on from this part of the galaxy long ago ("The Fifth Race"). Perhaps, they assume, someone moved in after they left – a civilization totally unlike theirs. This is hearsay, of course. The world was not necessarily ever inhabited by the Ancients, simply because the Stargate address came from their database.
  • At first look (images sent back from the M.A.L.P. probe), Daniel did not think that this civilization is even remotely connected to Earth history. It appeared incredibly advanced and developed, indicating that it was probably not a culture transplanted from Earth within the last few thousand years (as are many of the populated worlds they encounter).
  • The alien signal, or entity, piggybacked itself on the M.A.L.P. radio signal, enabling it to return through an outgoing wormhole. Though wormholes are one-way only for matter, radio signals may be sent back and forth ("Watergate"). This seems reasonable, since the entity is apparently energy-based. It seems fantastic, though, considering the fact that the entity reported that radio waves themselves harm its people.
  • The first thing that the entity did was to analyze human physiology – the infirmary's computer systems show that this data was being accessed. Once determining that it could find refuge inside a human brain, it examined the social structure of the base and determined that Carter was someone invaluable to them – someone whom they would never kill, even if she was possessed by the entity. Survival was truly its one goal all along.
  • Carter and the team of engineers got the computer systems working long enough to dial out and communicate with all off-world S.G. teams – apparently before the M.A.L.P. room mainframe was discovered. The teams were told to stay put.
  • Hammond seems to reveal to Jack that he knows about the Colonel's feelings for Major Carter, reminding him not to let that stand between him and a hard decision (to terminate Carter's life for the safety of Earth and the base). Though O'Neill's feelings were brought out into the open in "Divide and Conquer," General Hammond was not present at the time. He may have inferred the information from any mission reports turned in after O'Neill and Carter were cleared as not being za'tarcs; but more likely, Hammond has simply been astutely observing the two and their relationship over the past four years.
  • It seems amazing that Sam's disembodied consciousness would be able to be sent to the make-shift computer mainframe in the M.A.L.P. room, considering that the system was entirely isolated from the rest of the base – and that the only access the entity had to the base systems when transferring Carter was whatever happened to be in the hallway. Apparently the M.A.L.P. room mainframe was not entirely isolated, since once there she was able to communicate her message ("I am here") with the entire base.
  • Dr. Fraiser didn't really know how to transfer Sam's consciousness from the computer system back into her body. Of course, there is no medical precedence. She (rightly) assumed that it might work to hook up Sam's head to the computer terminal with electrodes, providing a basic conduit – and allowing Sam to figure out the rest.


  • There is an emergency disconnect system located in the Gate Room, which shuts down power to the gate and forces the termination of an outgoing wormhole.
  • The S.G.C.'s computer data is archived at the Pentagon. It may be backed up as frequently as once every 24 hours.
  • The M.A.L.P. storage room is located on Sublevel 24 – four floors above the Gate Room.
  • The S.G.C. personnel database that the entity searched through included the following – probably fictitious – officers: Kent Matheson - Captain, SG-3 Lee Van Cleef - Master, SG-1 (Master Sergeant, perhaps?), possibly named after the actor Maureen O'Boyle - Major, SG-9 Richie Jarvis - Captain, SG-7 Kim Matheson - Captain, SG-3 The computer display cycles through each record several times. Note that Kent Matheson is Stargate SG-1's matte painter; Van Cleef is listed as a member of SG-1 and is shown with three different photos; and Maureen O'Boyle is the name of the host of the syndicated news magazine and gossip shows Extra and A Current Affair.
  • The coordinates to the entity's world have been locked out of the S.G.C.'s dialing computer.


  • Samantha CarterSamantha Carter - Because of her empathy with the alien entity and her desire to make contact with it, Sam was lured into a technological trap and taken over by the lifeform. It took possession of her body and subverted her consciousness, much as a Goa'uld parasite takes a host. But when O'Neill threatened to attack the alien's world if it didn't let her go, it transferred her consciousness to the computer system and allowed itself to be killed. Carter was eventually returned to her body. Certainly, the ordeal will have a lasting effect on her.

    Sam has a living will, requesting no extraordinary measures to sustain her life in case of accident.

    Carter's Air Force service number is 366349.
  • Jack O'NeillJack O'Neill - O'Neill made the greatest sacrifice in protecting Earth and the S.G.C.: he sacrificed not his own life, but the life of his fellow officer, friend, and the woman for whom he cares a great deal. Unsure of the entity's intentions, he shot Sam twice with a zat gun, killing the being inside her. But when her body was being kept alive by machine and her brain activity was absent, he sat by her side and would not let her go.

    In sacrificing Carter for the good of the S.G.C., and in wishing to destroy the entity rather than try to communicate with it, Jack stayed true to his character throughout the ordeal.

    O'Neill's Air Force service number is 69-4-141.
  • Janet FraiserJanet Fraiser - Fraiser struggled with being completely unable to save Sam's life, and it obviously got to her. Carter is not only a coworker, but a friend. Left with no course of action, she finally conceded to let Sam die.

    In medical matters, Dr. Fraiser may overrule those of any rank.
  • Daniel JacksonDaniel Jackson - Helpless in this situation, Daniel tried the only thing he knows – to communicate with the alien lifeform and try to reach an understanding. He was overruled by O'Neill, who refused to take the diplomatic approach with such a hostile being.

    Daniel also defended Sam's choice to try and communicate with the entity, though the choice nearly resulted in her death. "No matter what happens," he said to Jack and Teal'c, "Sam wasn't wrong to try and communicate with it." This says a lot about Daniel's character, which is focused on discovery rather than on protection or playing things safe.
  • George HammondGeorge Hammond - Hammond is apparently aware of Colonel O'Neill's personal feelings for Major Carter. But he trusts Jack not to let it interfere with his job, and has allowed them to continue serving together.


  • Was the alien world once populated by the Ancients?
  • Who lives on that world now, what kind of lifeform are they, and how long have they been there? If they are such a radically different form of life, do they use the Stargate?
  • How much of the S.G.C.'s data was lost in the system reformat?
  • Was the entity an artificial intelligence (an engineered "weapon," as it referred to itself), or a lifeform?
  • Is the entity completely gone?
  • How did Carter's consciousness find its way to the M.A.L.P. room computer?
  • How much damage did the M.A.L.P. cause to the alien world? Will they make another attempt to retaliate?
  • Will Carter suffer any after-effects from the alien possession, or from having her mind stored in a computer system?


  • "Entity" originally carried the working title "Child's Play," which even made it as far as the official MGM Web site and some TV listings.
  • "The premise was fairly standard but, like most every episode, what set it apart was what made it special for our characters – in this case, Amanda who got to go all Terminator, and Jack who is faced with a very tough call in dealing with the threat. What I found particularly interesting about this episode was that, after many stories in which Jack's military stance conflicts with Daniel's peaceful civilian position, invariably resulting in the latter being proven correct, the results are reversed here. Jack was right. He should have destroyed it when he had the chance rather than allow Daniel and Sam to attempt communication with the entity." (Writer-producer Joseph Mallozzi, in a post at his blog)