Two friends are invited for a weekend to a luxury island with their boss. The boss gets shot and nobody seems to notice, except for the two friends. In order not to become suspects of murder they treat the body as a puppet and make people believe he's still alive. The killer wants to do his job so when he is informed that the stiff is still alive he's got to shoot him again, and again, and again.
After four high school friends are involved in a hit-and-run road accident, they dispose of the body and vow to keep the incident a secret. A year later, they each start receiving anonymous letters bearing the warning "I Know What You Did Last Summer."