Gli inseparabili

A retired architect is killed in his bed. The housekeeper of the villa reveals that the man had no relatives or enemies; lately he was just a little nervous about the trip he was about to undertake, as he did every year, to Niagara Falls. A lawyer is also killed with the same weapon, and he too was about to leave for his annual trip to the falls. The two had known each other since school and shared their annual rendezvous with three other men. It is necessary to track them down as soon as possible: their lives could also be in danger. Or...