Mystery Date (1992)

Teenage Tom McHugh (Ethan Hawke) is madly in love with his ravishing next-door neighbor, Geena Matthews (Teri Polo), but becomes hopelessly tongue-tied whenever she's around. When his parents go away on an impromptu road trip, his suave law student brother shows up and begins coaching Tom on how to pick up women. Things are going great until Tom discovers a body in the trunk of his brother's car, and his perfect date with Geena takes multiple turns for the worse.