Louise, an ex-crime investigator turned professor, aid police in a serial murder case after receiving a culprit's challenge. With students, she probes victims' clinic where a van was spotted, intersecting Inspector Barbara's investigation.
A strangled man's body, tied to a chair in a bunny costume, found. Louise realizes the killer meant to humiliate the victim. Police narrow suspects to four gym members with motives. Louise infiltrates Valentine and Boris for information.