Star Trek: Voyager Season 2 Episode 15

Threshold

After finding a type of dilithium that can survive at a higher temperatures, Tom Paris comes up with the ingenious idea of attempting to cross the transwarp threshold in an attempt to find a way to get home faster. After a bumpy start and the help of Torres and Kim, they succeed in a holodeck simulation. When it is presented to Captain Janeway, she is impressed and gives them the go ahead to try it, but traveling faster than warp 10 has never before been attempted. The first run goes very well. Tom Paris manages to cross the warp threshold which means that the shuttle craft in which he is traveling exists simultaneously everywhere. But Tom then disappears and Harry is unable to find him anywhere within five parsecs. Tom somehow manages to return to Voyager through subspace, but there are unforeseen side-effects of his transwarp travel and Tom begins to mutate. The doctor tries to treat him with a type of radiation that will prohibit cell mutation, however this fails and Tom dies. To the Doctor's surprise, Paris is able to regenerate himself and wakes up a couple of hours later with two hearts! His body continues mutating, with new organs growing and others being absorbed back in to his body. Tom refuses any treatment, saying that this is the best thing that ever happened to him but deep down he is scared. A cure is found by exposing Tom to highly focused anti-proton radiation to destroy all the new DNA and allowing his original DNA to reassert itself. However, Tom breaks free from his restraints, kidnaps Captain Janeway, takes the shuttle craft to transwarp. Captain Janeway's DNA goes through the same mutagenic process as Tom's. When Voyager catches up with them on an alien planet three days later, Paris and Janeway have devolved millions of years and have mated, producing three offspring. Commander Chakotay recovers Paris and Janeway but makes the decision to leave their offspring on the otherwise unpopulated planet.