The appearance of the superior officer is- surprising, there's no denying that. At the same time, Zulf has been expecting him or someone similar to make an appearance. You couldn't leave a lower warrior to be your representative forever, after all. After the initial slight start, Zulf gives an obedient nod to the new face. There wasn't any plan to stay around, after all-

Then the group gets bigger and an abrupt change comes over him.

Anyone paying attention won't miss the way his shoulders get tense or how his skin gets all the paler, betraying the expression on his face that can be seen from the front- a deer caught in the headlights. Colin can likely pick up the fact that his heart is threatening to go out his chest. There's a belated pause before he turns his head to nod to Tris, not saying anything- his jaw is clenched shut. His hands are shaking too, nails dug into the back of one hand.