Cleveland Heep (PAUL GIAMATTI) is the manager and superintendent for the Cove Apartments in Philadelphia. Something of a lowly and modest man with a stutter, he lives on the grounds and spends most of his time making repairs for the various tenants. Among them is crossword puzzler master Mr. Dury (JEFFREY WRIGHT) and his son Joey (NOAH GRAY-CABEY); animal lover and former author Mrs. Bell (MARY BETH HURT); and intellectual recluse Mr. Leeds (BILL IRWIN).
Bodybuilder Reggie (FREDDY RODRIGUEZ) is only bulking up on one side of his body; Korean college student Young-Soon Choi (CINDY CHEUNG) lives there with her traditional mom (JUNE KYOKO LU) who doesn't speak English, while political writer Vick Ran (M. NIGHT SHYAMALAN) shares his place with his sister Anna (SARITA CHOUDHURY). The newest tenant is book and film critic Mr. Farber (BOB BALABAN) who seems to want to be left alone.
Believing someone's been swimming in the pool after hours and against the rules, Cleveland thinks he's caught the person, but he ends up falling into the pool and nearly drowns. He's saved by a mysterious woman named Story (BRYCE DALLAS HOWARD) who says she's a sea nymph known as a Narf from the Blue World. She's there to cause an awakening in a certain person, but doesn't know who that is. Complicating matters is a wolf-type creature known as a scrunt that lives in the grass and can't be seen by humans except via a mirror.
Cleveland never questions this or his learning from Young-Soon that various people there are predestined to assist her in avoiding the scrunt, find the chosen person and then prepare to return to her world via an eagle that will transport her. Accordingly, he then sets out to help her by assembling those people so that she can succeed at the task at hand before time runs out.