Not only is Ms Alpha scary as all hell. She is also proving herself to be quite the strategist. Collecting Yumiko's arrows from the cemetery, possibly the bridge and using them to lure Luke and Alden into their trap. I am guessing that Alpha and company happen upon the bridge where Lydia was taken prisoner. She (Alpha) sees her daughter's discarded mask and knife and realizes that she has been taken. The first thought is "a mom wants to find her child". Ehhhh I wonder if Alpha wants to find Lydia because she is her child or rather because she does not want to risk Lydia giving away any information. I tend to think it is the latter. Of course this also creates many questions. Was Alpha part of the group in the cemetery? If not how did she know about the deaths and cemetery? Was Lydia part of the group in the cemetery? Is it safe to assume that the whisperer we saw unlatching the gate brought the cemetery intel back to Alpha and that is how she knew about the arrows? How did Alpha know that Luke and Alden were from the community that Michonne's search group originated from?