Dan Mahowney [Philip Seymour Hoffman] has a secret life. At his work in the bank he is known as a quiet employee with a modest lifestyle and a sweet but plain girlfriend called Belinda [Minnie Driver]. But Dan is a compulsive gambler, who has plunged himself into debt with no way out. When he is promoted to asssistant manager his new responsibilities give him the authority to transfer funds in and out of the bank. As Dan is struggling to cover his debts, he starts to abuse his position and move huge sums of money to non-existent accounts and into his own casino account. When his debts hit seven figures his deception is hard to hide - from the authorities and from Belinda. 'Owning Mahowney' is based on a true story.