‘I Know What You Did Last Summer’: Not Knowing Who Plays the Killer Helped Filming Feel ‘More Natural’ for Fiona Rene

Kevin Williamson turned Lois Duncan’s novel I Know What You Did Last Summer into a horror movie in 1997. The franchise expanded with two more horror films released in 1998 and 2006. But now, the story is getting another revamp thanks to the Amazon Prime series I Know What You Did Last Summer (IKWYDLS). In each iteration of Duncan’s story, the biggest question is, “Who is the killer?” 

Showbiz Cheat Sheet spoke with Fiona Rene, who plays Lyla in the Amazon Prime show. Rene shares what it was like being kept in the dark as her character searches for the killer.

Fiona Rene as Officer Lyla in the Amazon Prime series 'I Know What You Did Last Summer'
Fiona Rene | Michael Desmond, Amazon Studios

‘I Know What You Did Last Summer’ tells the story of a mysterious killer 

In the I Know What You Did Last Summer novel, the killer is Bud, who the main character Julie starts dating a year after she and her friends accidentally run over a cyclist. As fate would have it, Bud is the brother of the young man killed in the accident. 

The I Know What You Did Last Summer film flips the story slightly. Instead of the person involved in the hit and run being killed, the character is incapacitated. Played by Muse Watson, Ben Willis becomes a crazed fisherman hellbent on seeking revenge against the four kids who struck him with their car and left him for dead. 

Ben Willis returns as the fish-hook-wielding killer in I Still Know What You Did Last Summer. This time, Ben’s killing spree takes place in the Bahamas. Later, in I’ll Always Know What You Did Last Summer, Ben returns from the dead and goes on another killing spree, attacking a different group of teens. 

‘I Know What You Did Last Summer’ cast didn’t know who the killer was while filming

During the 2021 New York Comic-Con, IKWYDLS creator Sara Goodman spoke about the upcoming Amazon Prime series. “I didn’t want anyone to know [who the killer is] until the last minute,” Goodman said (via Polygon). “Even on a subconscious level. I didn’t want anyone to be reacting to that actor differently. I felt like it was very important that everybody not know until they had to know — which made everybody crazy.” 

Madison Iseman looks into a mirror with lipstick that reads 'I Know What You Did Last Summer' in a still from the Amazon Prime series
Madison Iseman | Michael Desmond, Amazon Studios

According to Goodman, her phone still contains multiple texts from actors surmising who they thought the killer could be at various points during filming. But for Rene, who plays local cop Lyla in the series, being kept in the dark was for the best. 

Fiona Rene found herself ‘genuinely searching’ for the killer on the set of ‘IKWYDLS’

During our Zoom call with Rene, we had to ask what it was like not knowing who the killer was while filming I Know What You Did Last Summer. Was it a constant state of stress? Did Rene constantly question her character and wonder if she was the killer? 

“I felt that it was great personally for my own character work,” she tells us. “As Lyla — as the police chief, you don’t want to know. You want to genuinely be searching.” 

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Rene admits being kept out of the loop allowed her to play the role of a genuinely invested cop. “It felt very natural,” she adds. “It felt very realistic for Lyla to consistently be looking at everyone as a possible suspect and not really have anyone jump into her mind frame of who it is.”

As Rene explained, not knowing who the killer was in I Know What You Did Last Summer forced her to consider all of the clues and evidence. Ultimately, this influenced the decisions Rene’s character makes in the show. 

You’ll have to watch I Know What You Did Last Summer on Amazon Prime to find out who the killer is this time. Stream new episodes beginning Oct. 15.