In the early 1970s, a young artist named Ewa Zawadowska finds the body of her 70-year-old uncle Antoni, whom she had been caring for. The old man had been strangled with a nylon stocking. A quarter of an hour earlier, she had seen him alive and in high spirits. He died while Ewa was out shopping for a short while. Returning from the store, she met an elegant stranger on the stairs, who could have been the killer. The militia launches an intensive investigation into the case. Lieutenant Edward Radoń, who is leading the investigation, determines that the only thing missing from the apartment of the deceased, who was an antique collector, is a 16th-century pirate map. Its true value is unknown, but it allegedly contained information about a treasure hidden on the island of Tobago. It's an unusual lead, reminiscent of Robert Louis Stevenson's adventure novels, so can it be taken seriously?