Accidentally on Purpose

At an office party, Billie anxiously waits with her best friend Olivia for the arrival of James, her ex-boyfriend and boss at the newspaper, where she works as a film critic. She is hoping that when he sees her, James will realize that not committing to her while in Paris was a mistake.

Flashback - a month earlier. For their third year anniversary, James takes Billie to the top of the Eiffel Tower and hands her a small black bag. Thinking James is going to pop "the question", Billie says, "I do" but then finds a marzipan candy instead of an engagement ring inside the bag. Billie, envious of the other couples getting engaged around them, discloses her desire for a more permanent relationship then walks out on James, who doesn't share her sentiment.

Back at the party, Billie quickly escapes out of the party with Olivia after seeing James arrive with Kate Moss. Billie drinks her sorrows away at a club with her sister Abby and Olivia. As she goes to the bar, she meets Zack, who is a cook, and his friends, and engages in a few banters with them.

After some flirting and dancing, Billie agrees to go home with Zack back to his apartment. Zack shows her around his place and offers her a taste of his ravioli, which she loves. They make out, and then Zack carries her to his bedroom. The following morning, Billie leaves a post-it on Zack's forehead and sneaks out of the room, only to find his friends playing video games outside.

She leaves the house and meets up with Abby and Olivia, expressing her exhilaration over her recent sexual encounter. A few hours later, she and Zack go at it again. Five weeks later, Billie takes a pregnancy test, that turns out to be positive.

While her sister is thrilled for her, Billie is distraught, yet decides to keep the baby. That evening, she goes to the restaurant where Zack works and tells him about the pregnancy. Without much hesitation, Zack agrees to share with the responsibility.

Later on, Zack accompanies Billie to her first doctor appointment, where she undergoes an ultrasound. They both get excited after Dr. Roland shows them the fetus in her womb. Billie then offers Zack to move in temporarily to her place.

Zack, with his friend Davis in tow, brings his things to Billie's apartment. Meanwhile, Billie defends her reason to Olivia and Abby for letting Zack stay at her place. She tells them that even if she and Zack are living together, she has set boundaries in their unusual setup.

The next day, Olivia and Billie continue discussing the complex scenario Billie finds herself in. James overhears them talking and notices something different about Billie. James tells her that he finally wants them to live together, which to him means alternating between staying at his place and Billie's apartment.

Zack suddenly arrives at the office to bring Billie some salad for lunch. James discovers her secret about the baby, has a heated conversation with Zack, and threatens to use his martial arts skills on him. James walks away after Billie accuses him of not caring about her.

That evening, Billie comes home to catch Zack and his friends drinking beer and hanging out in her living room. After walking into the kitchen and seeing they broke the refrigerator door, Billie airs her frustrations to Zack. She asks him to move out, but upon seeing the nursery Zack and his friends prepared for the baby, Billie softens up and takes Zack back in.

Before going to sleep, Zack, lying on the floor, and Billie, tucked in bed, voice their joy over having met each other. And as Zack rambles on about the food items he can prepare for breakfast, Billie blurts out "I love you" to him.