A 15-year-old aspiring actress wanted so badly to retrieve her cell phone from a locked room at a Tribeca house party that she climbed onto the fire escape to get in through a window — and fell to her death, police and other sources said Monday.

Beacon HS sophomore Imogen Roche slipped and plunged five stories from the apartment building on Reade Street near West Broadway in Manhattan around 11 p.m. Sunday, according to law-enforcement sources. She landed on her back and was rushed to Bellevue Hospital Center, where she died.

“This is heartbreaking, literally heartbreaking,” said one of the teenager’s neighbors, Vicki Water. “She was adorable, and [her dad] was an amazing father, a single parent.”

The owner of the apartment was out of town, and some of the teens at the bash were drinking, police said.

At some point, Roche climbed from a window onto the fire escape to try to get her phone — then lost her balance as she was maneuvering into the window of the locked room, according to cops.

Friends knew the teen as quiet and smart with a knack for theater arts.

“In class, she was very attentive, disciplined and a good listener. Very bright,” said one former teacher. “She was very close to her dad. They were always together.”

Her father, Theseus Roche, works as a director of after-school programs for Manhattan Youth. He’s a writer, actor and a member Screen Actors Guild.

At the Tribeca building, the windows leading to the fire escape are built in a dangerous way, said a former resident who lived in a sixth-floor loft.

“I remember the ledges were really high on the window. When I was there, I always wondered, if there was a fire, how would I get out,” said Eugene Yoo, who lived one floor above where Roche fell. “It would actually be a big climb [from the fire escape] to the window.”

Roche’s parents couldn’t be reached immediately for comment Monday.

Additional reporting by Reuven Fenton and Natalie O’Neill