After last week's episode, we have a lingering mystery: Who said help?
Norman Reedus revealed last week that it was not Glenn on the other end of that radio, so the popular assumption is already ruled out.
First, let's take into account that the first half of season six hasn't exactly been linear. We've seen flashback episodes. We've seen episode that run side by side, before their predecessor.... The timeline has just been all over the place.
If it were an Alexandrian on that radio, we would have to assume Daryl, Sasha, and Abraham's adventure took a little longer than we may have initially thought and we haven't seen the chaotic event in Alexandria which warrants a desperate call for "Help" on the radio.
In the comics, the walls of Alexandria fall eventually and a massive walker herd floods the streets. If this is the case on television, it's not unlikely someone is hiding from walkers and responding to Daryl in hopes the he and his two buddies come to help fight the dead. We've seen Alexandria be attacked by the living, as well, so it's not impossible for the Wolves to have returned or even a new group to have appeared and are posing a significant threat.
Did Carl ever leave the Safe-Zone? He talked about it with Ron and Rick wanted to go find him but we never found out if he left. If he did, you can bet he ran into trouble, making him a candidate for needing "Help." Maybe he saved Enid and ran into some foes.
Of the characters we've met so far, the only likely remaining candidate is Dwight (that jerk who took Daryl's bike and bow). Assuming Dwight got captured by the men from whom he was fleeing, he may have been filled with instant regret for leaving Daryl behind and is now asking for help, again.
A popular theory, however, is Jesus. Tom Payne was cast as Paul Monroe earlier this year, so we know his debut as the man they call Jesus can't be too far away. If he's going to debut in the first half of season six, he'll have to hurry up. His introduction in the comics was just slightly after the point in time where the show is in relation the comics' story timeline.
The Walking Dead airs Sundays at 9 PM ET on AMC.