Mari cannot stand watching her convenience-store-owner husband struggle with constant shoplifting, so she consults the security company where her older sister Anna's husband works. Worried about Mari's safety, Anna decides to join her inexperienced sister as a plainclothes store detective. The pair catch several shoplifters and begin to relax, only for Mari to detain the wrong person. Outwitted by someone they were certain they had seen stealing, the sisters discover that a major organized theft ring is operating behind the scenes...