Theresa „Tree” Gelbman wakes up on her birthday on Monday, September 18th in the dorm room of classmate Carter Davis after a drunken binge the previous evening. Tree goes through the day being self-centered, dismissive and condescending to her fellow classmates and previous hook-ups, ignoring her father’s invite to a restaurant, throwing away a birthday cupcake given to her by her roommate Lori, and having an affair with Dr. Gregory Butler, her professor. That night, while going to a party, Tree is lured into a tunnel where she is murdered by a hooded figure wearing a mask of the campus mascot.
Tree wakes up the next morning back in Carter’s bed with the previous day’s events repeating. Unnerved, she relives the day and avoids the tunnel, instead returning to her sorority house for a surprise party. However, while hooking up with her classmate Nick, the masked killer murders him before killing Tree once more. Tree realizes she is in a time loop and tries to avoid her death by barricading herself in her room. However, she is murdered again when the killer hides in her bathroom.
During the next loop, she relays her story to Carter, who suggests that she take advantage of the loop in order to figure out who her killer is. She spends the next loops trailing several suspected classmates, all of which end in her death as she is stalking the current suspect.
Watch Happy Death Day 2017 online subtitrat in romana HD. On the next loop after being bludgeoned by a baseball bat from her previous death, Tree passes out shortly after waking up. She awakens in the hospital where she learns she has retained damage from her other murders. Tree escapes the hospital room only to be chased by her killer until she manages to flee in Butler’s car. While driving, she is pulled over by a police officer and volunteers to be arrested in order to be spared. However, the killer runs down the officer and sets her car on fire, burning Tree to death and sending her through another loop.