Emma is a young woman who has always been terrified of her birthday. When she was a child, her family was killed in a terrible accident on her birthday, leaving her as the only survivor. Since then, Emma has refused to celebrate her birthday, even as she grows older.
On her 21st birthday, Emma's roommate and best friend, Alice, decides to throw her a surprise party to cheer her up. However, Alice and the other guests are oblivious to the fact that Emma's fear of her birthday is not just superstition - there are real dangers lurking in the darkness.
As the party gets underway, strange things begin to happen. The lights flicker, objects move on their own, and eerie whispers can be heard. As the night wears on, Emma's fear grows stronger and she begins to realize that something sinister is happening.
The horror of what happened on her birthday as a child is already lurking in the shadows, but now there is something else too. Emma discovers that a vengeful clown, who was responsible for the accident that claimed her family, has been waiting for years to get revenge on her.
As the night grows darker, Emma and her friends must confront the evil clown and face their deepest fears if they have any hope of surviving and putting an end to the clown's terror once and for all.