"What if I told you everything that happened to you yesterday was a false memory? How would you know the difference?"
— Lt. Col. Cameron Mitchell
During a visit to the planet Galar, the team is introduced to a technology that allows memories to be implanted into a person's mind; Mitchell hits it off with Reya Varrick, one of the scientists working on the device, only to be accused of her murder when she ends up dead after they spend the night together. He claims to remember killing her, and the team must find a way to prove that the memory has been implanted and is not really his.
"Collateral Damage" provides examples of the following tropes:
- An Arm and a Leg: It's revealed through one of Mitchell's childhood memories that his father was a test pilot who had both legs amputated following a bad crash.
- Compliment Backfire:Varrick: You know how it is with scientists. We spend so much time in the lab, I think that's where we feel most comfortable.Mitchell: In your case I find that hard to believe.Varrick: Are you suggesting I don't work as hard as my colleagues?Mitchell: No! No, God, no... That was supposed to be a compliment.Varrick: Guess I'll have to take your word for it.
- Dark and Troubled Past: In order to prove that the memory of him killing Varrick is false, the scientists need to compare the memory to a true memory of Mitchell's where he was in a similar situation, which in this case means he would need to have knowingly killed an innocent. "Fortunately", Mitchell has such a memory; he once bombed a convoy that he had been told was a military target, only to get an update after he had fired the missile but before the blast that the convoy were actually innocent refugees.
- Enhance Button: Morrell discovers an anomaly in Mitchell's memory, which Mitchell sees as a blurry, misshapen reflection in a mirror. Mitchell asks if he can "clean it up", which he does, revealing the identity of the killer.
- Frame-Up: Varrick's ex-husband Morrell frames Mitchell for the murder by erasing his own memories of the event and implanting them in Mitchell's mind, assuming that he would claim diplomatic immunity and the whole thing would be swept under the rug.
- Hired to Hunt Yourself: After erasing his memory of the murder, Morrell is distraught by the death of his ex-wife and works harder than anyone to bring the culprit to justice. He winds up revealing himself as the true killer after helping Mitchell identify an abnormality in the implanted memory.
- If I Can't Have You…: Mitchell deduces that Morrell never got over Varrick after their separation and killed her out of jealousy after seeing her leave the party with Mitchell.
- In Medias Res: The opening of the episode shows Mitchell waking up and being arrested the morning after the murder, before going back twenty-four hours earlier to show How We Got Here.
- Karma Houdini: After Morrell is outed as the real killer, the Emissary has his memories re-erased and allows him to continue working on the memory project believing that Varrick died in an accident, since he's now the most qualified scientist available.
- Married to the Job: Varrick claims that her marriage fell apart as a result of her obsession with her work.
- My Greatest Failure: It's revealed that Mitchell accidentally bombed a convoy full of refugees due to faulty intel back when he was a captain, something he's never been able to forgive himself for.
- Narrative Profanity Filter: Landry's comments on the team's mission reports at the end of the episode:Landry: Not sure I've ever seen language like that used in an official Air Force document before.Mitchell: Sorry about that, sir.Landry: Oh, you should have seen what Colonel Carter and Dr. Jackson wrote.
- Red Herring: To draw suspicion away from Morrell, it's implied throughout the episode that the Emissary had Varrick killed due to their disagreements over the military having control of the project. However, this is subverted somewhat once the truth comes out, and the government decides to wipe Morrell's memory (and make him believe Reya died in an accident) rather than let the truth come out, "for the good of the project" (due to Morrell being the most qualified person to run it after his ex-wife).
- Sex Signals Death: Varrick is killed after taking Mitchell home, though it's not clear if they actually have sex or not; all we see is them kissing in the kitchen.
- Transferable Memory: The memory device is developed from Goa'uld technology to allow the transfer of memory from one person to another. The Galarans seem to want to use it primarily for teaching purposes, and Landry mentions that the Air Force is keen to get its hands on it for similar reasons, but Daniel is wary about the ethical implications from the get-go and a lot of the shine wears off for the rest of the team after it's used to frame Mitchell for murder.
- Wham Shot: Mitchell seeing Morrell in place of his own reflection in the mirror while looking for inconsistencies in his memory of the murder.
