apartment building in downtown glendive. paying, thing, thing past the ever listening cell towers. . and suddenly the cop had some homework to do. >> i didn't know who marty was. i had no idea. >> but he knew from the towers that marty larson was the third man to put himself near susie casey during the night she vanished. which is why he said call the state department of investigation. and soon after marty return from glendive, agent lee johnson found himself standing outside marti's apartment. staying at this freshly washed cleaning. then video again, courtesy of the police. >> it was obviously very clean on the exterior because it had been through an automatic car wash. the interior of the vehicle had heavy compensation on the vehicle. >> what did you find inside? >> the vehicle had been shampoo to, the carpets had been clean. when you get into the cargo area in the back of the van, it had been vigorously cleaned out with some type of solution.