Princess Principal/Recap/S1/E01 Case 13 Wired Liar

Quoting from Wikipedia: "Eric, a scientist, seeks to defect to the Commonwealth. Ange and her fellow spies Dorothy, Beatrice, Chise, and Princess smuggle him to safety inside the Queen's Mayfair School, a prestigious academy where they are posing as students. However, Eric also requests that they bring his little sister Amy as well. Ange and Beatrice go to investigate Amy, and discover that she is suffering from Cavorite poisoning, which requires an expensive procedure to cure. However, after observing several clues and Eric's odd behavior, Ange concludes that Eric is in fact a double agent meant to lure them out into the open. Her suspicions are confirmed when Eric attempts to send a carrier pigeon to his handler. Dorothy, Beatrice, and Chise capture Eric's handler while Ange takes Eric to a secluded park, where she exposes his plan. Eric admits he was approached by the Duke of Normandy, who said Amy's operation would be funded if in return Eric agreed to fake his defection. Ange has Eric sign a life insurance policy before executing him. A week later, Eric's body is found and the money from the insurance policy is used to pay for Amy's operation."