Eagle Eye Agency (1982)

From the box:

Players are Private Eyes, all working for Eagle Eye Agency, gathering clues in Big City to solve the mysteries. Shadow suspects, do legwork, gradually work up a case. Everyone plays a key part. It's not who wins, but rather can we all solve the mystery? Thirty-nine original cases are provided. When you have exhausted these cases, you can extend the game by using the Mystery Maker Kit included to create more of your own cases. Your ingenuity is your only limit... But what is special about the game is not only solving those mysteries, but also the co-operative sleuthing. Expect lots of dialogging over Case Theories, Puzzling Clues, and even the Final Solution!