“Latent Image” is episode eleven of season five of Star Trek: Voyager.
The Doctor is holoimaging the crew. When he gets to Naomi, she’s worried because they didn’t do this last year. Last year, the Doctor didn’t realise what an exciting tool the holoimager is in search of medical knowledge. Naomi is still worried; the Doctor reassures her that all the crew are being done as part of their annual check-up. He explains what he’s doing, and perhaps goes a little too far as the Doctor has to be holimaged by Naomi to reassure her.
With Harry done, the Doctor asks him if he’d like to see what he looks like from the inside out. An image of Harry appears, from the bones out. Something the Doctor sees puzzles him. Harry has scar tissue at the base of his skull. From an operation. Somebody performed neurosurgery on Harry – and that someone was the Doctor. He developed the procedure himself. Harry says he doesn’t remember having the treatment. The Doctor doesn’t remember performing it.
The Doctor heads to see the captain in her ready room. He’s finished with the crew’s annual physicals – all except for her. As usual. He’s making a house call. He fills her in on the health and then mentions the holoimaging he’s added. He’s already discovered something. 18 months ago, he performed complex neurosurgery on Harry Kim, but he doesn’t recall it. Nor does the captain. And it isn’t in the medical database. Yes, it’s possible that he misinterpreted the holimager’s results; the Doctor is checking on that. He’d like a diagnostic run on his own program. Harry and B’Elanna are busy; they’ll get to him next.
The Doctor heads to astrometrics and basically guilts Seven of Nine into helping. He explains the situation and she agrees to help him run a self-diagnostic in an hour. When Seven arrives at sickbay, she activates the Doctor. She’s here to assist as agreed; a preliminary diagnostic shows his suspicions are correct. The Doctor doesn’t even remember asking. Or what happened after the yearly physicals. Harry’s holoscan has been deleted, as has the Doctor’s short-term memory buffer. Someone is trying to keep him from remembering what happened 18 months ago.
Back then, the Doctor was taking holimages every day. He and Seven head to the holodeck to view the images from that period. They have been deleted, but Seven thinks she can partially reconstruct some of them. They show the mess hall, with a birthday party for an ensign the Doctor doesn’t remember. He, Harry and said ensign on a shuttle, which is attacked by an alien. Seven thinks she can partially reconstruct the Doctor’s memories. He remembers the party, the ensign covered in blood and her and Harry in sickbay, both dying. And an alien shooting all three of them, but not affecting the Doctor.
This is reported to the captain and Tuvok. The Doctor believes there was an attack on Voyager and their memories were erased. The ensign, Jetal, was she an alien intruder? The Doctor is certain they are in immediate danger, because someone erased his memories. The ship is ordered to be swept for intruders and a scan for cloaked ships run. Captain Janeway wants the Doctor to deactivate for his own safety, so they will know if someone tampers with him again.
In sickbay, before deactivating himself, the Doctor decides to duplicate his memory files from the last 48 hours and, if his program is altered without his authorisation, to restore them and reactivate him. And he sets up the holoimager to record anyone entering the room. Which someone does, and deletes the files. The Doctor reactivates when they leave and, using the holoimager, discovers that the intruder was the captain.
The Doctor heads to the bridge where the Chakotay and Tuvok are both telling the captain she’s wrong about a sumo match. It seems Tuvok is a fan of sumo. The Doctor accuses the captain of tampering with his program. And realises Tuvok is in the conspiracy as well. He demands to know why.
The captain tells the Doctor to accompany her to her ready room. He accuses Janeway of manipulating his program and tells her not to deny it. She has no intention of denying it. The Doctor was damaged during the attack and suffered a conflict in his programming that couldn’t be resolved, so they had to deny the Doctor access to the memories.
The Doctor isn’t happy he was tampered with. Nor is Seven of Nine, for that matter, heading to speak to the captain in her quarters in the middle of the night to discuss the ethics of the matter. Which makes Janeway herself think again about the decision she originally made.