CENTEREACH, N.Y.—Police say a bank teller in Long Island, N.Y., had a simple question for a would-be robber: Are you serious?

The skeptical teller’s question was apparently enough to spook the female suspect, who fled the Roslyn Savings Bank in Centereach late Thursday afternoon without a dime.

Police say she walked into the bank located inside a supermarket and handed the teller a note demanding cash and threatening to open fire if the teller didn’t comply.

That’s when the teller expressed her crime-fighting dubiousness and asked if the suspect was serious. Police say the woman left without ever showing a gun.