Inspector Megure asks Mori Kogoro for help to expose his subordinate, Detective Sawatari, whom he suspects of having an affair. The trigger is a café receipt for a "Lady’s Meal Set," which Sawatari ordered with an unknown woman while his wife was away. Additionally, footage from a police camera shows Sawatari in front of a jewelry store and a flower shop. Megure fears Sawatari could lose his job over a scandal.

Ran and Conan join the investigation. The analysis of the flowers reveals they are chrysanthemums – typical for grave visits. Conan discovers that Sawatari did not make any purchases but instead picked up an engagement ring at the jewelry store, intended for the girlfriend of his deceased colleague Sametani. Sametani died in the line of duty but could no longer deliver the ring. Sawatari acted on his own to fulfill Sametani’s last wish, risking professional consequences.

The apparent "evidence" of an affair turns out to be a tragic gesture: Sawatari accompanied the grieving woman to the grave and helped her receive the ring. Megure, relieved by Sawatari’s integrity, promises to address the rule violations internally. The episode ends with a hint about the next case, in which the Detective Boys shoot a film and Kogoro unexpectedly directs.