Newly arrived in Chicago from the South Pole, Mr. Pin--a penguin and a detective--is quickly friends with the proprietor of ""Smiling Sally's Good Food,"" her niece Maggie, and the loyal truck drivers who are partial to her cinnamon buns. And none too soon--Sally is threatened with extortion. Mr. Pin's quick thinking, the truck drivers' help, and enough chocolate ice cream to encase the gangsters until police arrive save the day. Pin also undertakes two other cases here: a stolen Picasso is traced to a bakery, and a chocolate pigeon conceals jewels intended to provide food for the homeless. Lively plotting; staccato, deadpan delivery in whimsical parody of Dashiell Hammett; an economical style and carefully controlled repetition of ideas and phrases (""Big cities can have big hearts,"" Mr. Pin thinks, more than once); and an engaging hero combine in these three genuinely funny, brief mysteries.