As usual, there are twelve "collections" in this series. A few of the mysteries:
- In "Unique is Where You Find It", the Widowers try to puzzle out what element of the periodic table is most unique to a particular college professor who has challenged their guest.
- In "The Envelope", the Widowers are asked to speculate on the significance of an envelop tucked into the jacket of a spy.
- "The Recipe" is a locked-room mystery that the Widowers attempt to solve.
All in all, though, superb as usual. Asimov is the master.