to whidbey island. to the police. yes, to the island county sheriffs. i felt guilty i was giving up my friend. but i knew something had to be done. josh mankiewicz: within days of that call, detectives mark plumberg and mike beech were sitting face-to-face with both their tipster, bill hill, and their suspect, the artist formerly known as buck naked. [music playing] coming up, the interrogation gets tough. you know what you've told bill. the guy is falling apart over the guilt he's carrying around because you told him what you did. josh mankiewicz: will jim crack? or will detectives realize they have the wrong man? when "dateline" continues. for this product is overwhelmingly positive. this toothpaste sensodyne repair & protect can actually repair and protect sensitive teeth. and as long as they brush twice a day, everyday, then they can expect to continually have that reparative layer of protection against sensitivity. sensodyne repair & protect has clinical evidence showing how effective it works. i absolutely think that dentists are going to want to

>> uh, because you're from -- whidbey island?> would it surprise you that i've been talking to him almost daily for the last week and a half? >> yeah, it would surprise me. >> i just wanted to see a reaction. up until that point he was playing it pretty cool, and i think i got the reaction i was hoping for. it kind of deflated him a little bit. >> it's truth or dare time, jim. you know what you told bill. he's your best friend in the whole world. the guy is falling apart over this, literally falling apart over the guilt he's carrying around because you told him what you did. >> i don't buy that for a minute. >> if revealing bill hill as their source was intended to shock jim huden into confessing, it failed. with no murder weapon, no warrant and no authority to make an arrest in the state of florida, the detectives had to let their primary suspect go free. were you worried at all about bill hill? now you've disclosed he's the source of all this. >> we made sure before we went back to washington that bill understood that we had to