The Host
Series: Star Trek: The Next Generation
Airdate: May 13, 1991 | Year Set: 2367
Season 4, Episode 23
Summary
While on a peacekeeping mission to the Peliar system, a Trill ambassador begins a relationship with Dr. Crusher, but when he is injured in a surprise attack, he must confess to the doctor that his body is merely a host for a parasite.