Molly Bowen is driving from a press tour for a horror film which she was an actress in. She is arriving on the two-year wedding anniversary to her husband Will whom she met on the first horror film that he wrote for the franchise that made her a star. During her drive, she has a conversation with her friend Evie about how she is tired of Will's anniversary "surprises." She comes home to find dinner being made by her loving husband. He tells her to take her usual "zen bath" to acclimate to coming home and dinner will be ready soon. She comes down after to find dinner set, but no Will. He accidentally surprises her when he comes back in from the "workshed" outside with a bottle of wine. They sit down to dinner and talk about her shoot. He presents Molly with a gift after the meal. She opens it to reveal a brand-new electronic tablet and sees a button marked “Surprise” on the screen. She presses it and it reveals a “live feed” of her friend Timothy Conrad lying unconscious inside a thick plex-glass coffin located outside in their “Work Shed.” It is the same one that was built as the property master for her last shoot.
Will tells Molly that he has discovered her affair with Timothy. Molly denies it. Molly tries her phone and it doesn’t work. Will tells her he has changed the WiFi Password and killed her boosted signal. She won’t be able to call out. Molly tries to get to Timothy by heading out the back door. She can’t open the security lock. Will has changed those, too. Molly heads for the kitchen for a weapon, but Will has emptied it of anything that would harm him. She tries throwing a chair through the front window to escape. He replaced them with polycarbonate. He tells her that she will have to play the game he made for her. She asks why she should. Will tells her he has poisoned them both with Colltrix. It is slow-acting and will take full effect in one hour. Molly goes to the kitchen to try and find a weapon, only to find out that Will has cleared it out. He doesn’t believe her and tells her that he has taken their mutual love of “game night” to the “next level” by hiding five items throughout the house that prove her affair. He will be giving her “riddles” for each one so she can try and find them. If she finds them all and can disprove them, she wins, and he will give them the antidote to the poison and turn himself in. If not, all of them will die. Will is about to start and asks Molly: “Sound like fun?” Molly angrily agrees to start the game.
Will gives Molly a riddle, starts the first song as a timer and she starts the scavenger hunt of their lives. Throughout Act II, Molly will have to find: Blackmail Photos, an Email to a friend, Her Tablet with Saved Pictures of Her and Timothy, and an Order from a "Couples Store" with Questionable Items. Every item is found through a riddle. Every search is timed to a favorite song from "Molly's Mix" from her Amazon Music. Will pushes through every search with bullying questions about the nature of her relationship with Timothy and every item is defended with truth by Molly. She is nevertheless rattled and asks for a bathroom break after question number two. Molly is able to retreat to the upstairs bathroom where she remembers there is a small window that can be cracked open above the toilet. She does so and is able to get her hand out with the phone. She sees it has one bar. She texts Evie in order to try and get help. They are able to have a brief exchange before Will is knocking on the door. Evie tells her she is on her with help!
Molly returns to the game and during her defense of item number three, there is a knock at the back door. It is Evie! Molly is saved! Only to find out that Will has convinced Evie of Molly's infidelity, and she has been in the "shed' monitoring Timothy's vitals in the coffin. Will doesn't tell Molly that he has told Evie this is all a way to scare Molly into being faithful. Evie gives Will a kit with needles and the antidote... This is the "help" that she meant... and returns to the "work shed;" leaving Molly to finish defending the third item.
Will gives the riddle, starts the music and Molly searches for the final item. There are only ten more minutes left until the poison takes hold and Timothy runs out of air. She finds it and makes her last defense. All the facts speak to the fact that she is telling the truth. Will hesitates but can't deny her answers. But it doesn't matter to him. He injects himself with the antidote and tells him that he is going to watch her die and Timothy will suffocate. He'll "take care" of Evie in the same way he "took care" of the blackmailer before. Molly starts to beg for her life and Will simply does not care. He is enjoying the show. Will's vision begins to blur and the last thing he sees is Molly smiling.
He wakes up inside of the plexiglass coffin in the warehouse. Standing above it are Molly, Evie, and Timothy. Molly tells Will that Evie told her his plan weeks ago and that she wasn't going to have anything to do with scaring her. Molly then told Timothy and he was in on it as well. By agreeing to be a part of it, Evie was able to make sure that: the poison that Will put in the wine was a placebo, she was able to monitor Timothy's help and she was able to put a sleeping agent in the antidote needles.
Molly tells Will that she never had an affair and never would have. He should have just trusted her. She starts a song on Will's phone, presses repeat, then duct tapes it facing him onto the lid of the coffin. Molly wishes him: "Good luck in getting out" and starts to leave with Timothy and Evie. The last thing that Will sees is Molly opening the garage doors, turning around, and smiling as she closes the doors behind her - all the while N*Sync's "Bye Bye Bye" plays