// _populate_stair_distances.  Assuming we're not on stairs, that

            // _populate_stair_distances or (c) we're trying to travel to
            // a non-traversable square. Assuming we're not on stairs, that

            // If deltadist is zero, travel is trying to occur to a non-seeded
            // square, so bail.  This can happen if trying to travel to a wall.

                deltadist = -1;

                return (-1);