Last tango in Paris

An American widower, grieving over his wife's unexplained suicide, hooks up with an 18-year-old French female after a coincidental meeting in an apartment, which they are both interested in renting. Spontaneous chemistry and sexual magnetism draw them into an illicit affair as they agree to rendezvous at their "shared" apartment for lots of. ahem...cardio exercise, involving a mattress, a dead rat, and butter. It'll all make sense midway through the movie. A big rule in their "relationship," or, perhaps, tryst (being a better word) is that they agree not to reveal any personal information about themselves; not even names. And as such, the lovers continue their journey through sexual role playing, emotional raping, and reverting to childhood memories. The ending is surprisingly dramatic.