Inspector Steve Trent tracks the stolen Cortez emerald, last pilfered by a murdered gangster.

This early docudrama uses dramatic reenactment, working models of early flying machines, and archival footage to trace man's attempts to fly from ancient times through the 1930s.

Derwent dreams up an unbreakable alibi for a murder. Once the crime is attempted, it then falls to Pember and Brace of Scotland Yard to sort things out.