FBI Special Agent Sarah Ashburn (Sandra Bullock) is a methodical investigator with a long-standing reputation for excellence – and arrogance. In contrast, foul-mouthed, hot-tempered detective Shannon Mullins (Melissa McCarthy) goes with her gut instincts and street smarts to remove criminals from the streets of Boston. Sparks fly when these polar opposites have to work together to capture a drug lord, but in the process, they become the last thing anyone expected – buddies.