When Phoebe's study group casts a love spell that turns three ordinary pets into attractive men for 24 hours, the Charmed Ones must stop the angry "Manimals" before they ruin Valentine's Day for everyone. As the newly made men terrorize the campus, searching for a way to remain human, it becomes clear that not all of their animal traits were lost in the transfer.
Meanwhile, Piper finds herself caught between loyalty to her boyfriend of the moment, Dan, and the lingering love she feels for now-mortal Leo. Dan's jealousy grows as it becomes apparent that Piper is not sure what she should do. Leo makes his feelings clear, as he shows all intentions to fight for the woman he loves.
The newly unemployed Pru finds that doing nothing is not all that it's cracked up to be, growing bored in a hurry. She teams with Phoebe to stop the Manimals before they kill the girls who made them, and before they capture Phoebe in a last minute bid to become permanently human. All comes to a conclusion when the Manimals crash the Valentine's Day party at Piper's club. In a failed attempt to turn the Manimals back into their non-human form, Phoebe turns everyone in the club into an animal, turning the party into a glorious outtake from Dr. Doolittle. All ends well when Phoebe turns everyone back into human form and the police capture the now permanently human bad guys.