Lassiter (also known as The Magnificent Thief) is a 1984 American heist spy film starring Tom Selleck and Jane Seymour. The movie was made to cash in on Selleck's popularity as the character Thomas Magnum in the television show Magnum, P.I., but it failed to return its budget at the box-office on release. The Magnum, P.I. connection is perhaps most clearly seen by the movie poster tagline: The Magnum Man Hits the Big Screen with a Vengeance.