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I Know What You Did Last Summer2021

TV-MA Horror Thriller Mystery 8 Episodes

One year after the fatal accident that shattered their graduation night, a group of teenagers finds themselves bound by a dark secret — and stalked by someone who knows exactly what they did. Everyone is hiding something, and uncovering the wrong secret could be deadly.

Season 1

Episodes

About the Series

Someone Remembers

A year has passed since a graduation-night celebration ended in a fatal car accident on the cliffs above their island town. The group of friends who covered it up thought their secret died with the truth — until a killer in a fisherman's slicker starts picking them off one by one, each attack a message that someone knows exactly what they did. As twin sisters Allison and Lennon and their friends race to uncover who's hunting them, they're forced to confront the buried resentments, betrayals, and secrets that have been quietly poisoning their friendships since long before that night — and to realize that in this town, everyone is guilty of something.

Episodes 8
Release Year 2021
Language English
Country United States
Genre
Horror Thriller Mystery
Starring

Cast

Madison Iseman
Madison Iseman
Allison / Lennon
Brianne Tju
Brianne Tju
Margot
Bill Heck
Bill Heck
Bruce
Ashley Moore
Ashley Moore
Riley
Ezekiel Goodman
Ezekiel Goodman
Dylan
Sebastian Amoruso
Sebastian Amoruso
Johnny
Fiona Rene
Fiona Rene
Danny
Cassie Beck
Cassie Beck
Courtney
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Verified Information

Cinelux Editorial Standards: This I Know What You Did Last Summer series page contains verified information sourced from official Amazon Studios records and Wikipedia. We confirm the writer and executive producer (Sara Goodman), production companies (Amazon Studios and Sony Pictures Television, in association with Original Film and Atomic Monster), lead cast (Madison Iseman in a dual role as twin sisters Allison and Lennon, alongside Brianne Tju, Bill Heck, and Ashley Moore), original premiere (October 15, 2021, on Amazon Prime Video), and episode count (8 episodes in a single season). Our team has cross-referenced the series' basis in Lois Duncan's 1973 novel and its Oahu, Hawaii filming location. Every detail is fact-checked for streaming audiences.

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Frequently Asked Questions

One year after the fatal car accident that haunted their graduation night, a group of teenagers find themselves bound together by a dark secret and stalked by a brutal killer. Everyone is hiding something, and uncovering the wrong secret could be deadly.

I Know What You Did Last Summer consists of 8 episodes in its first and only season, which premiered October 15, 2021 on Amazon Prime Video.

The series stars Madison Iseman in a dual role as twin sisters Allison and Lennon, alongside Brianne Tju, Bill Heck, Ashley Moore, and Ezekiel Goodman.

Yes — all 8 episodes of I Know What You Did Last Summer are available to stream in HD on Cinelux.