I Know What You Did Last Summer ending explained: Who dies, who lives and who is the killer?

I Know What You Did Last Summer premiered nationwide on July 18, 2025. Directed by Jennifer Kaytin Robinson, it is the fourth installment in the franchise following I Still Know What You Did Last Summer (1998).

In this installment, a new group of young friends is targeted by a Fishman killer who wants to get back at people who hurt them in the past. While being followed by a masked attacker, secrets are revealed, and only a few people make it to the end.

Disclaimer: This article contains spoilers for I Know What You Did Last Summer. Reader's discretion is advised.

The story starts with a fatal accident on the side of the road involving a group of friends. When a truck swerves off the road due to their reckless behavior, they decide to cover it up instead of helping the injured driver. 

After a year, they are being chased by a killer with a hook who knows their secret. As the killings happen they realize that the scenes of horror are a lot like a killing spree that happened 28 years ago. In the end it turns out that Stevie, a friend in the group, is the main killer. She did it to get back at the people who killed her boyfriend Sam in the accident. Another person from the past, Ray turns out to be the second killer.

At the end of the movie, Teddy, Grant, Milo, and other characters are dead, but Ava, Danica, and Julie are still alive. Ray was revealed to have been involved before he died.

The fatal car accident that started I Know What You Did Last Summer

The story begins when a group of five friends—Ava, Danica, Milo, Teddy, and Stevie—cause a horrific car accident on a dark night. Teddy (played by Tyriq Withers), after making a string of bad choices, stands in the middle of the road, making a truck coming the other way swerve and crash off a cliff. 
The driver dies in the crash, and even though people try to save him, the truck eventually falls into some rocks below. The friends don't want to get help, so they decide to lie about what happened and trust Teddy's powerful father, Grant (Billy Campbell), to keep them out of trouble. This sets the stage for a year of fear as they are stalked by an unknown killer.

Who survives in I Know What You Did Last Summer?

A few characters are still alive at the end of the movie. The main character, Ava survives her fight with Ray and is saved by Julie. Danica, who was thrown off the boat during the scene, ends up hurt but alive on a nearby beach. As Ava and Danica talk about what happened, they realize that Stevie is still alive, even though it looks like she died when she fell. 

The Fisherman returns: The Killer strikes

One year later, Danica receives a cryptic note reading, "I KNOW WHAT YOU DID LAST SUMMER." The friends are stalked by a masked figure wearing the iconic Fisherman costume, carrying a hook and speargun. Everyone in the group and the people nearby are killed by the killer, including Wyatt, who is engaged, and Tyler, who is a true-crime podcaster. 

The friends quickly figure out that they are being sought for their part in the fatal accident from the previous year. They only have one chance left: ask Julie James (Jennifer Love Hewitt) and Ray Bronson (Freddie Prinze Jr.), who lived through the first massacre, for help.

The twist reveals that Stevie is the Killer 

As the body count rises, the remaining friends—Ava, Danica and Stevie—attempt to flee on a boat. But Stevie, the friend who seemed to be innocent turns out to be the mastermind behind the killings. Sam Cooper was the driver who died in the accident and Stevie had been seeing him. 

Stevie is going to get back at them. She was also mad that they left her to deal with the aftermath of the tragedy since they knew she couldn't pay for a lawyer. Stevie had been planning her revenge for a year, pretending to be one of the victims and staging the killings to make it look like someone else did it.

Stevie's main goal was to get the friends to pay for what they did and she planned to kill Ava and Danica to do it. But just as she is about to kill Ava, Ray shows up on a smaller boat and seems to save them. Once Stevie and Ray got into a fight, Ray shot Stevie, making her fall into the ocean. 

The second killer: Ray's true identity

Just when it looks like the nightmare is over, Ray turns out to be one of the killers. He had been working with Stevie, and his part in the killings comes from a deep-seated feeling of being hurt and betrayed. 

Ray was fed up with the constant attempts to erase the violent past, including the killings that happened 28 years ago. Ray helped Stevie with her killing spree because she wanted to get back at people who wanted to hide the past. He was taking advantage of the situation to get back at the person who hurt him using Stevie's anger as a weapon.

When Ray locks Ava in his bar with the intention of killing her, it shows how betrayed he really is. But just as he is about to attack, Julie, who lived through the first massacre, shows up to stop him. Ray says that he killed because he was sad, the town was trying to forget its violent past, and he wanted justice. Ava shoots Ray with a harpoon when she figures out that he is really the killer. This ends Ray's reign of terror.

I Know What You Did Last Summer (2025) is running in theaters now.