Farscape/Recap/S04/E13 Terra Firma

Season 4, Episode 13:

Terra Firma

The crew of Moya and the humans start to learn more about one another. As Crichton reconnects with the people in his life, he tries to encourage the people of Earth to unite in their efforts to master space travel and join the larger universe. Unfortunately, the American government is more concerned with learning the secrets of advanced alien technology for its own use, and Crichton's family are aware of just how much he's changed during his time in the Uncharted Territories.

Crichton's debate about whether or not to stay home or return to Moya reaches a head when Grayza's creature stows away on a transport pod, kills several people (including D.K. and his wife) and attacks the Crichton family during Christmas celebrations. The creature is killed, but Crichton realises he can't stay on Earth because he's still being hunted. Before the crew leaves, Crichton says a proper goodbye to his father and receives a gift from his sister: their mother's engagement ring, for him to give to... someone.