Colonel Cameron Mitchell awakens in a confused state. Images of him bludgeoning a woman flash though his mind. He examines blood on his hands. Security personnel seize him and haul him into an adjoining room where the woman lies in a pool of blood. Mitchell is arrested for murder.

Twenty-four hours earlier, Mitchell was the test subject as the Galarans, led by chief scientist Dr. Reya Varrick (the murdered woman), demonstrate their memory technology – developed from a Goa'uld memory device they have been studying for one hundred years. Capable of inserting one person's memories into the mind of another, the machine gave Mitchell the memories of the Emissary as he congratulated Varrick on being named to lead the memory device project. It is an effective first demonstration of the technology, which the Galarans hope will help them to advance more quickly by easily passing on knowledge.

Back at Stargate Command, General Landry and SG-1 discuss the trip to Galar. As they debate the merits and dangers of the memory technology, Carter reveals that the Galarans want help with hyperdrive technology. A trade relationship seem immanent, as Landry says that the Joint Chiefs are salivating over the prospect of training jet pilots in mere days.

At a subsequent reception to honor the scientists, Mitchell chats up Reya while the rest of SG-1 debates the merits and dangers of the memory device with the Emissary. Dr. Marell, Reya's colleague, speaks privately with her. Reya then loudly confronts the Emissary about the military taking over her project. Observing the discussion, Mitchell approaches Reya. He ends up, at her invitation, agreeing to walk her home.

In her apartment, Mitchell recalls having been there before – courtesy of his implanted memories. He ascertains that Reya was married, but lives alone. They have a drink, and are soon kissing.

Daylight dawns and Carter, Jackson, and Teal'c visit the Emissary's office for help in locating Mitchell. The Emissary reveals that Mitchell has been arrested for Dr. Varrick's murder, citing various items of evidence ... and Mitchell's own confession.

Visiting Mitchell in his cell, Jackson, Carter, and Teal'c quickly realize that Mitchell's mind has been tampered with; the murderer has framed the Colonel and used their technology to implant the memory in his mind. The Emissary offers to release Mitchell and send him back to Earth, in order to preserve the negotiations. Despite his lack of knowledge about the Galaran judicial system, Mitchell refuses to leave without clearing his name. He also wants to learn the truth and have the horrific memory of the murder removed from his mind, but he refuses a memory replacement.

While Mitchell remains on Galar, the rest of the team briefs Landry. They quickly return with Carter agreeing to remain with Mitchell while the project scientists attempt to ascertain if his murder memories are false. Meanwhile, Jackson and Teal'c will conduct their own investigation.

Back in the memory project lab, Carter arranges for a sample of Mitchell's blood that was taken when he was arrested to be sent to the S.G.C. for corroborative tests. She grills the scientists, Drs. Marell and Amuro, about who they think killed Reya. They suspect the planet's military leaders, since Varrick was going to do everything she could to prevent the military take-over of their work.

Colonel Mitchell is hooked up to the machine as they search his memory for key moments in his early life. He recalls childhood memories of the first time he saw his father, a test pilot, after crash injuries forced the amputation of the man's legs at mid-thigh. Mitchell also relives a subsequent memory during which his father resolves to walk again.

Comparing these memories with the murder memories three times, no evidence of an implant can be detected – and the scientists start to suspect that Mitchell may have committed the murder after all. Dr. Marell, who it turns out was married to, but separated from, Reya, refuses to continue. When the blood sample tested by Stargate Command reveals that Mitchell was stunned before the blood was drawn, the scientists are persuaded to continue.

In order to continue, Mitchell must summon a memory with emotional resonance akin to that of the murder. He recalls the horrible day he was ordered to bomb a truck convoy, only to learn later that it was a convoy of innocent refugees. Comparison establishes, finally, that the murder memories are false. Determined to find out who did kill Reya, Mitchell relives the murder a number of times again. Eventually, he finds the murderer's face in a mirror and realizes that one of the scientists, Dr. Marell, killed his ex-wife.

Confronted, Marell is bewildered and puzzled. Dr. Amuro establishes that Marell killed Reya and gave the memory to Mitchell, then replaced the memory in his own mind – thereby removing his own link to the crime, and freeing himself from the guilt of murdering the woman he once loved.

In a final meeting, SG-1 learns that the memory technology has been used to remove any knowledge of SG-1 and the murder from Dr. Marell's mind, in order that he may continue his work with the device.

Home on Earth, Mitchell is preparing to go off duty when Landry comes to the locker room to check on him. Mitchell reveals that he almost resigned because of the bombing, but it was his father's courage that helped him move forward. Looking at a photo of his father, Mitchell flashes back to that moment – one memory he can happily hold on to.