Similitude

The episode opens at a funeral aboard Enterprise. Days earlier, an attempt to push the engines to warp 5 goes wrong and leaves Trip Tucker in a coma. Phlox proposes growing a mimetic symbiote, a duplicate of Trip with a lifespan of about two weeks, whose neural tissue could be transplanted to save him, though the procedure will kill the donor. Archer agrees. The duplicate, named Sim, grows rapidly from baby to adult, inheriting Trip's memories, personality, engineering skills and feelings for T'Pol. As the operation nears, Sim reveals he knows of an experimental treatment that might extend his life, which Phlox had kept from Archer because it was unproven. Sim desperately wants to live, but after thinking about Trip's sister, killed in the Xindi attack, he accepts the procedure. T'Pol kisses him before he goes to sickbay. The transplant succeeds, Trip recovers, and Archer pays tribute to Sim at his funeral.