King of California(2007)

You've got to believe in treasure to find it.

Charlie gets released from an insane asylum and moves in with Miranda, the young daughter he left behind. Charlie believes that there is treasure hidden beneath the local Costco, so he puts together a plan to unearth the loot. By convincing Miranda to quit her job at McDonald's and instead work at the wholesale store, he is able to obtain a key. Although Miranda is skeptical, she helps her father with his irrational quest.