Night Slaves (1970)
When asked whether she found it difficult to play the character of "Naillil," Tisha laughed at memories of her youthful self when she told Tom Lisanti, "No, because I think I was an alien back then." But that's okay. These were really very nice aliens.
Night Slaves was Tisha's "body snatchers from outer space" movie, but Tisha and Andrew Prine (playing her space captain "Noel") weren't really body snatchers, just body borrowers. See, their spaceship broke down, and (since these were bodiless aliens, pure-spirit types) they needed to borrow some earthling bodies for a few nights to do the manual labor of getting the thing fixed up. So Naillil borrows the body of one Annie Fletcher, while Noel borrows the body of fellow-townsman and not-quite-right-in-the-head Fess Beany.
Now, where the aliens came up with those names is, "Naillil" is "Lillian" spelled backwards, and "Noel" is "Leon" spelled backwards, and that all has to do with this automobile accident in which Clay Howard (played by James Franciscus) killed an elderly couple named Leon and Lillian, and Noel can't take over Clay's mind because of this metal plate that Clay's had in his head ever since the accident, so Clay (who's just a tourist anyway, vacationing with his soon-to-be-ex, Marjorie, played by Lee Grant) is the only guy in the whole town who realizes that there's some body-snatching (oops, "borrowing") going on, so Noel has to make it look like Clay is just hallucinating all this in some kind of a guilt-trip over killing Leon and Lillian, and . . . .
And . . . . if that's all a little confusing, don't worry about it, because it's really a pretty standard sci-fi plot, maybe even a little trite, but it works, and that's because of the performances by James Franciscus and Lee Grant, backed up by Andrew Prine, Leslie Nielson as Sheriff Henshaw, and a really fine ensemble supporting cast, along with skillful camera work under director Ted Post.
And Tisha, of course. What really makes Night Slaves most stand out above a rather conventional plot is the ethereal (and elvishly flirtatious) way in which Naillil makes her appearances and disappearances on the ghostly scenes. There's a believability to Tisha's performance that makes it understandable that Clay Howard would decide to abandon his own body to join Naillil as the alien's spaceship departs for its destination that perhaps only space-captain Noel knows.
Note: James Franciscus starred as the tough-minded, idealistic high-school English teacher John Novak on the 1963-1965 NBC-TV drama series Mr. Novak, on which Tisha made a guest appearance in the "Firebrand" episode (April 13, 1965). He died of emphysema on July 8, 1991.