Describe the plan Perry creates to avoid climbing those thirteen steps?

From the text:

But that was not what Perry really believed; he believed what he'd written Don Cullivan, with whom he now corresponded regularly: his crime was "unforgivable," and he fully expected to "climb those thirteen steps." However, he was not altogether without hope, for he too had plotted an escape. It depended upon a pair of young men that he had often observed observing him. One was red-haired, the other dark. Sometimes, standing in the Square under the tree that touched the cell window, they smiled and signaled to him - or so he imagined. Nothing was ever said, and always, after perhaps a minute, they drifted away. But the prisoner had convinced himself that the young men, possibly motivated by a desire for adventure, meant to help him escape.