The movie revolves around Julia Banks, who finally moves in with her fiancé David Connover after being in a long-distance relationship. However, David's ex-wife, Tessa, seems less than thrilled about the new relationship and continuously creates problems for Julia through phone calls and surprise visits. Along with Tessa, Julia's haunting past also seems to catch up with her, making it tough for her to settle in.
As Julia tries to adjust to the new life, Tessa's tactics become more dangerous, and she will stop at nothing to get David back. Through a series of events, it is revealed that Tessa has a personality disorder and is willing to hurt anyone who gets in the way of her obsession of getting David back.
Meanwhile, Julia is trying to keep her own secrets hidden and is struggling to gain David's trust while being surrounded by Tessa's tricks. Julia's friend, Ali, helps her uncover Tessa's unstable behavior and tries to convince David that his ex-wife is dangerous.
In a crazy climax, Tessa's true colors are revealed, and it is a race against time to save Julia and David from her wrath. The movie brings the constant undercurrent of tension and suspense, leaving the audience on the edge of their seats.