While flying from New York to London US Federal Air Marshal Bill Marks (Neeson) receives text messages from an anonymous sender who is threatening to murder a passenger every 20 minutes until millions of dollars are deposited into an unnamed bank account.

Marks faces a race against time to find and restrain the person responsible but when the bank account is found out to be in his name he is accused of being the hijacker. As victims are claimed, Marks discovers a bomb on board the aircraft which only exacerbates his predicament.

Can he find the culprit in order to save the remaining passengers and prove his innocence?