On the evening of his high school reunion, Bill visits his old "hangout' to meet up with his high school friends. The place is slow, and without customers, but Bill strikes up a conversation with a young and charming waitress. When Bill's old classmates show up and begin to relive the "old days", they realize that Bill has much more on his mind than a casual visit. Matterhorn explores the nature of the past, present and future, and how they each influence each other. Can a small difference change everything, or is only one future inevitable?