Fog of doubt (The Gregg Press mystery fiction series)

Rosie, the naughty little nymphet around whom Christianna Brand weaves her witty and mysterious web, recounts to her family a series of fibs that results in their supposing the unfortunate suitor, Raoul Vernet, to be her base seducer. On a night of dense London fog, with everyone alibied, Raoul is discovered having been hit over the head with a blunt instrument.