  We show that the cop number of every generalized Petersen graph is at most 4.
The strategy is to play a modified game of cops and robbers on an infinite
cyclic covering space where the objective is to capture the robber or force the
robber towards an end of the infinite graph. We prove that finite isometric
subtrees are 1-guardable and apply this to determine the exact cop number of
some families of generalized Petersen graphs. We also extend these ideas to
prove that the cop number of any connected I-graph is at most 5.
