  We solve an open problem posed by Michael Biro at CCCG 2013 that was inspired
by his and others' work on beacon-based routing. Consider a human and a puppy
on a simple closed curve in the plane. The human can walk along the curve at
bounded speed and change direction as desired. The puppy runs with unbounded
speed along the curve as long as the Euclidean straight-line distance to the
human is decreasing, so that it is always at a point on the curve where the
distance is locally minimal. Assuming that the curve is smooth (with some mild
genericity constraints) or a simple polygon, we prove that the human can always
catch the puppy in finite time.
