Paul Giamatti, a famous American actor, is going through an existential crisis. He's trying to find himself, struggling to even find the right tone during the rehearsals for his next play, Uncle Vanya by Anton Chekov.
He then hears about a private laboratory offering a highly intriguing service: here clients can put their souls in storage. The laboratory takes away the troubled soul and can replace it, quite easily, with another available in their catalog.
The proposition is attractive and the actor decides to let go of his soul. This sets off a chain reaction whose scale he could never have imagined.