An interesting variant of the cops and robbers pursuit-evasion problem is presented. The motivation for the problem comes from the need to monitor a network of roads leading to a protected area. In this paper, an unmanned aerial vehicle (UAV) is searching for a slower moving ground vehicle on a road network that has been out-fitted with unattended ground sensors (UGSs). The UGSs are communication constrained and can only relay observations of the ground vehicle when the UAV visits them. Furthermore, the UAV does not have on-board capability to detect and identify the evader and therefore must investigate the UGSs to learn the evader's location. This scenario leads the UAV's control actions to depend on partial information. A sufficient condition for guaranteed isolation of the intruder is provided along with the corresponding pursuit policy. Since the policy is non-unique, we select a policy that provides the least time to capture among all policies with the guarantee.