Slaking a thirst for dangerous games, Kathryn challenges her stepbrother, Sebastian, to deflower their headmaster's daughter before the summer ends. If he succeeds, the prize is the chance to bed Kathryn. But if he loses, Kathryn will claim his most prized possession.
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."
On a US nuclear missile sub, a young first officer stages a mutiny to prevent his trigger happy captain from launching his missiles before confirming his orders to do so.