Well I know this doesn't make any sense, but I thought maybe (and just MAYBE) Campman kidnapped Clem's parents and stole the walkie from them, so he could also attract Clementine to him by telling her he has her parents with him (Clem not knowing he may have kidnapped them). I remember that Diana said on the answering machine that Ed had a little "incident" with some crazy guy near the hotel. We all think it was a walker (it's most probably since he went ill after that), but what if it was some kind of fight with Campman and he had just been hurt by him? And then some days later Campman kidnapped Ed and Diana and they're both in the Marsh House? Maybe Diana could finally send a last message to Clem without Campman knowing to warn her ("Clementine baby, if you hear this, call the police..."). And now maybe he has both of her parents plus Clem in the Marsh House. It's only a theory, and I know it doesn't make much sense doing all that stuff just for Lee (maybe Campman is the State Senator that Lee "killed", who may had survived? Or even his ex-wife with some kind of voice changer device?), what do you think?
P.S: Sorry, I just realized I posted this in the wrong place, could someone move it to the Spoilers forum? >_< Sorry about that.