Maigret's Revolver

They ran into cloud cover as they approached the French coast and flew up above it. Through a break in the clouds a little later, Maigret caught a lucky glimpse of the sea, sparkling as if covered in silvery scales, and fishing-boats trailing a wake of foam.
His neighbour leaned across amicably to point out the white cliffs, explaining:
'That's Dover ...'
When Maigret's prized gun goes missing, he must travel to London on the trail of a troubled young man on the run.