In Denver, accountant Sandy Patterson (Jason Bateman) buys identity theft protection from Diana (Melissa McCarthy), a con artist, over the phone and reveals all of his personal information. At work, after Sandy clashes with his obnoxious and bullying boss, Harold Cornish (Jon Favreau), he receives a phone call that reminds him he has an appointment at a salon in Florida. Confused, he puts it out of his mind when co-worker Daniel Casey (John Cho) suggests they and several others leave Cornish’s company and start their own firm; Sandy agrees to join them.
When paying for gas, Sandy’s credit card is declined, and the clerk cuts it up. As the credit card company tells him that he has spent huge amounts of money in Florida, he is arrested for missing a court date there. At the police station, Detective Reilly (Morris Chestnut) determines Diana has stolen Sandy’s identity. The situation worsens when cops ask Daniel, now his boss, about Sandy’s possession of drugs. Reilly says Sandy’s name was used to buy drugs from someone named Paolo (Jonathan Banks). When the cops say they can do nothing due to jurisdictional issues unless the identity thief is in Denver, Sandy offers to retrieve her and convince her to clear his name, despite his wife, Trish’s (Amanda Peet) concerns.
Sandy finds Diana at the salon in Florida, but when he confronts her, she steals his rental car. Finding her address in her abandoned car, he investigates her house, which is full of merchandise and stolen credit cards. The pair scuffle; before Sandy can handcuff her, criminals Marisol (Génesis Rodríguez) and Julian (T.I.) burst in, angry that Diana gave Paolo bad credit cards. After Sandy and Diana escape, Sandy tells her about his plan to restore his reputation, and she agrees to help. Meanwhile, a skiptracer (Robert Patrick) is dispatched to track down Diana for a substantial bounty. Because their IDs are identical, flight is impossible, and they travel to Denver by car.
After traveling through several states, the skiptracer catches up to the pair and captures Diana. A chase ensues; she knocks him unconscious, and Sandy rams his van off the road. When Sandy’s rental car gets plowed and totaled by an oncoming semi, they take the skiptracer’s van, with him tied up in the back. When it overheats, they continue on foot through a forest. Sandy discards his pants when he finds a snake in them, and Diana accidentally knocks him unconscious when another bites his neck. Sandy wakes at a bus station, and Diana says she carried him until she flagged down a truck. As the next bus to Denver leaves in three days, Sandy uses money hidden in his socks to buy a $200 car from an auto wrecking yard. For gas money, the pair con an accounts processor and steal Cornish’s identity to create new credit cards. Meanwhile, Marisol shoots the skiptracer, and the criminals continue their pursuit of Sandy and Diana.