In 1917, on New York City's Lower East Side, Baruch Rosenfeld invites a beggar to join his family for the Passover Seder. However, his good deed backfires. Baruch, his wife Rebekah, and their children Nathan, Jacob, and Sadie are trapped in time. They don't age, they can't leave their three-room apartment, and the outside world believes they disappeared without a trace.

A hundred years later, the apartment building is now the Tenement Museum. Esther Luna, an educator for the museum, sees Sadie at the window. Esther goes to the apartment but finds it has been empty for decades. She hires Rabbi Meir Poppers, a kishef macher (magician), to solve the mystery of the girl at the window.