The Doctor deals with the memory of a patient lost.
The Doctor discovers that Harry Kim underwent brain surgery that only he could have performed, yet he has no memory of it, and some of his files have been erased, including images of an ensign named Ahni Jetal. Digging further, he learns that Janeway and the crew deleted the memories after a crisis some time earlier.
In an attack on a shuttle, Kim and Jetal were both badly wounded, and the Doctor had time to save only one. He chose Kim, his friend, and was then torn apart by guilt over whether friendship had swayed him, a conflict his programming could not handle. When the memories return, he breaks down again. Seven of Nine argues that he deserves the chance to work through it as a person would, and Janeway agrees, sitting with him as he recovers. The fifth-season episode is a major step in the debate over whether the Doctor is more than a program.