The Film: Face/Off is simply a film about Nicolas Cage and John Travolta swapping faces.

One's a goodie and one's a baddie, but when they swap faces, of course, things get confusing.

If it sounds ridiculously far-fetched, that's because it is.

The Affair: When Castor (the baddie) comes home to Archer (the goodie)'s wife, he assumes the identity of Archer. Therefore, Fake-Archer's relationship with Real-Archer's wife is technically an affair, even if wifey's not aware of it.

Long-Term Relationship? Not likely - the penny was bound to drop sooner or later and Real-Archer is too volatile to keep in the dark for long ("GIVE ME BACK MY FACE!!!")