A woman who was stabbed by a maniac at Grand Central Terminal on Christmas Eve said he came up from behind and punched her — and that no one around her came to her aid after he plunged the knife into her throat.

If you ride the New York City subway system, don't expect anyone to help you if you're getting attacked. They're calling it the "Penny Effect,"

Jason Sargeant, 28, of Brooklyn, was arrested after the violent spree Tuesday night, in which he allegedly stabbed a 26-year-old woman in the throat and slashed a 42-year-old man in the wrist in separate attacks.