A biochemist, Allen, who's unlucky in love creates a compound to turn polyamorous leanings into monogamous ones. He injects his lesbian best friend, Marcia, to make her stop cheating on her wife, Sarah (who is bi).

But when Sarah finds Marcia's new fixation on her to be suffocating, Marcia insists Allen give Sarah a dose too, which backfires when Sarah falls for him. While avoiding Sarah's obsessive advances and hiding the whole situation from Marcia, Allen must team up with a rival scientist, Lisa, for whom he's falling, to set things right.

Their romance blossoms, but is hindered by Lisa's extreme OCD, which requires kissing through a face mask. Things get even more complicated when Allen's boss, Jim, inadvertently gets injected too and also falls for him. And all the while, the overzealous Safety Officer Nancy is investigating. If she catches Allen, he faces going to prison for an FDA violation... although any kissing there surely won't be through a mask.