The other group was not in the prison, Kirkman said so on the Talking Dead.

A few plot holes but good sode overall.

 1. Rick left the gate open when he walked outside, leaving plenty of opportunity for sniperguy to get inside and climb the outer tower. Like Glenn bitched about earlier in the episode "Who's on guard duty?"

2. Tyrese and his group only had one revolver with maybe 3 rounds of ammo left. Would you go running towards a firefight if you were nearby and heard that going off? Me either, and something tells me Tyrese's group wouldn't have lasted two years on the road by just popping up to be more targets for the Governor and goons.

3. I think Andrea might actually be the one that turns Woodsbury against the Governor in the end. The Governor has given her a lot of power and free reign, and she seems to be ruling the town without the veiled threats the governor had been doling out to the towns people previously. 

4. The Dixons needed to go on their little walkabout to clear a few things up between them. Daryl has grown beyond Merle's influence. We saw that with the family at the bridge, and even the subtle argument as to what creek they were crossing (with Daryl being correct in the end when the camera pulls back and shows the road sign). The only way Merle was getting into the prison was by helping save Rick's life. 

5. Cut off from the main entrance, Rick, Merle and Daryl may have to go through the opening in the back of the prison and finally find out what the hell is going on. This would also go a long way in Merle's favor if he helps out with this problem. 

Lack of understanding is not a plot hole!

man some of you dudes need an explanation for every tiny little detail!  Some shit just happens, it's totally plausible and you just don't need to walk thru every step!

for instance:  Isn't it part of the scare tactic by the Gov to get a guy in the tower and take the group by surprise when they least expect it?  Just cuz you were caught off guard too doesn't mean it's a plot hole, it means his plan worked!!

Great episode, for the record I have NO problems with it or the writing.......

And Sarah Wayne Callies is gawdamn beautiful!

we haven't seen the last of Tyrese, even if they didn't show his group for some of you insecure folk who need confirmation of existence in every episode, they were kinda busy showing us other stuff.........

 Anybody can be caught off guard by ninja mutants.

 Noah, did Kirkman say where Tyrese went to?

 Anyone want to bet that Daryl ends up killing Merle? Characterwise it makes sense. The Survivors have come to represent Daryl's family he never had and Rick the big brother he wished Merle was. Merle is going to put the group in danger and Daryl will protect his "real" family. 

Just a thought.

 Great episode, lots of good stuff buidling up to that bravura firefight. LOVED the Governor's rifle! Those Steyr bullpups are WICKED...
And I thought Hershel really stood out in this story, beyond the usual "poor old guy who lost a foot" vibe he's had lately. His attempts to keep both Rick and Glen from melting down and causing the group to shatter were very tense and exciting to watch, reminiscent of some of his stuff from last year.

 Hanso, 

On Talking Dead Kirkman said Tyrese and crew were not in the prison anymore, but they are 'around' and 'will pop up again'.

I loved the shot of the Yellowjack Creek sign that showed Darrel was right again.  Merle's not much good for anything except killing people and walkers.