Basically the guard captain tipped off the group about a nefarious plot going on. Ssarak and Meirin found a map on the robed man which more or less details various trade routes with certain locations marked off. The Commander and Ryo were thinking about how to approach it. For one this mission has dragged on for pretty long, so they want to preemptively take on the ambushers so they get the element of surprise and finish up the mission ASAP. This also saves us the time of having to do any negotiations and let's us go strait to the ass kicking. The only issue is that you all need to figure out your battle strategy and convince the caravan master to actually head towards the bad guys. 

Oh, and they want to bitch at Alaira for attacking a guardsman earlier that day. While they were going to attack you if you didn't bother them, Alaira picking a fight with them before they could hold them up meant that they could play the victim card while Alaira continues to look like a thug.