"The Host" is the 23rd episode of the fourth season of the American science fiction television series Star Trek: The Next Generation and the 97th episode overall. It was originally released on May 11, 1991, in broadcast syndication.
Set in the 24th century, the series follows the adventures of the Starfleet crew of the Federation starship Enterprise-D. In this episode, Doctor Beverly Crusher (Gates McFadden) falls in love with Odan (Franc Luz), a Trill mediator. But after he is mortally injured, she discovers that "Odan" is actually a symbiotic creature that lives inside a humanoid host body. Commander William Riker (Jonathan Frakes) volunteers to act as a temporary host, complicating the relationship between Crusher and Odan. The mediation proves successful, but after Odan is transferred to a new, female Trill host (Nicole Orth-Pallavicini), Crusher chooses not to continue the relationship.
At the time of filming, McFadden was seven months pregnant, resulting in filming techniques used to conceal her abdomen. A two-part makeup appliance was designed for the Trill host, as well as the symbiont itself, which was based on a caterpillar and an octopus. The Trill would subsequently return in Star Trek: Deep Space Nine, although the makeup was redesigned. "The Host" received a Nielsen rating of 11.3 percent during the first week of release in syndication. The ending of the episode has received a mixed reception, with Zack Handlen for The A.V. Club saying that the reaction by Crusher made "perfect sense", The filming of Gates McFadden's scenes was complicated by the fact that she was seven months pregnant at the time, requiring different camera angles than would normally be used. Jonathan Frakes, who played Commander Riker, explained later that "they would not address the fact that the actress was pregnant", Rush was not told which episode he was going to direct beforehand, other than that it was going to be a ship-based episode. which featured one of the earliest televised lesbian kisses.
The character of Odan would return in non-canonical Star Trek publications, including in the short story "First Steps" within The Lives of Dax anthology. It also made two appearances in licensed comics, first in DC Comics Star Trek: The Next Generation Annual issue four and then in Divided we Fall, a crossover between The Next Generation and Deep Space Nine published under the WildStorm imprint. as the intention was to retain the general look of a human. Air bladders were placed inside a fake abdomen to create the shot in which the symbiont appeared to move under the host's skin. A second fake abdomen was created for the surgery scene in which the symbiont is moved into Riker, which worked by having a crew member lie under the surgery table, pulling the symbiont into the opening using a concealed string. The design of the symbiont was based on a caterpillar with an octopus for a head, which featured a further air bladder in order to give the appearance that it was pulsating, and painted in fluorescent paint to glow when a black light was shone on it during that scene.
The Trill later recurred in Deep Space Nine, with multiple hosts of the Dax symbiont appearing on screen. The same makeup was initially used as in their originally appearance in The Next Generation, however after two days of filming with Terry Farrell in the prosthetics, she was sent back to the makeup department to change it. The shuttle set was the same one which had been used previously, with parts created for different episodes since work began in the first season episode "Coming of Age". In "The Host", it was named Hawking for the theoretical physicist Stephen Hawking.
James Van Hise, in his book The Unauthorized Trek: The Complete Next Generation, called the introduction of the Trill an "element crucial" to Deep Space Nine, but was critical of the decision to have Crusher not be interested in Odan once he had transferred to his new female host. This "apparent homophobia" was said to have resulted in the episode being "widely criticized" by David Greven in his book Gender and Sexuality in Star Trek. Keith DeCandido, in an article for Reactor, wrote it was difficult to give a fair review of the episode due to the Trill being explored in greater depth in Deep Space Nine, and the subsequent alterations made for that series compared to "The Host". He said more generally of the episode that the romance felt rushed, and he would have liked to see the exploration of Riker's feelings about his body being used to have sex with a friend. A further criticism was leveled at the ending, as Crusher's statements implied it was humans who have a problem with homosexuality and bisexuality rather than limiting it to be her own problem. He gave it a rating of four out of ten.
Nick Keppler, writing for Nerve.com, listed "The Host" as one of the "gayest" episodes of the franchise and described the twist at the end of the episode with the gender of Odan's new host as "sapphic". Zack Handlen gave the episode a rating of B+ in his review for The A.V. Club, saying that the idea at the core of the episode was better than the execution. But he said that the ending made "perfect sense" as he said that love wasn't solely spiritual but that "we fall in love with features, with shapes, with bodies, as well as with minds." He added that Odan's reaction was also right, as "everyone has a line, and if you love them, you won't ask them to cross it."
The first home media release of "The Host" was on VHS cassette, appearing on July 23, 1996, in the United States and Canada. The episode was later included on the Star Trek: The Next Generation season four DVD box set, released in the United States on September 3, 2002. The fourth season was subsequently released on blu-ray in the UK on July 29, 2013, and July 30 in the United States.