Melville's explanation of the Cornish Cliff Mystery was very simple when
he gave it. Yet it was an ingenious trick that the two criminals adopted,
and it would have completely succeeded had not our friends from the
Puzzle Club accidentally appeared on the scene. This is what happened:
When Lamson and Marsh reached the stile, Marsh alone walked to the top of
the cliff, with Lamson's larger boots in his hands. Arrived at the edge
of the cliff, he changed the boots and walked backwards to the stile,
carrying his own boots.
This little manoeuvre accounts for the smaller footprints showing a
deeper impression at the heel, and the larger prints a deeper impression
at the toe; for a man will walk more heavily on his heels when going
forward, but will make a deeper impression with the toes in walking
backwards. It will also account for the fact that the large footprints
were sometimes impressed over the smaller ones, but never the reverse;
also for the circumstance that the larger footprints showed a shorter
stride, for a man will necessarily take a smaller stride when walking
backwards. The pocket-book was intentionally dropped, to lead the police
to discover the footprints, and so be put on the wrong scent.