The Vault follows Thom (Highmore), a genius engineering graduate whose interest is piqued by the Bank of Spain. It's safe, built over 100 years ago, has no blueprints, and its security system includes an underground river that floods the safe room if breached. After learning that a legendary treasure will be deposited in the bank's safe, Thom masterminds a meticulous plan along with charismatic art dealer Walter (Cunningham) to break into it.