When Jacen actually let him in he was a little startled, but it didn't show on his face. He hadn't been expecting the government type to just let him in beyond the door where he could peer judgingly around his home from the outside. Mal couldn't help but raise an eyebrow when Jacen continued the hospitality and called him Captain. He decided to do what little he could as far as social formalness went and removed his arms from where his weapons were hidden. They went up to rest gently on his chest, crossed and uncomfortable.
"Came to see where River's been hanging about lately. Got her brother all crotchity you know. " He eyed Jacen pointedly and continued. It was obvious Mal didn't have much schooling in a formal sense, or many experiences in social settings where he wasn't required to fight for his life. "Do you know how many gorram times a second he brings up his sister and how not fun it is for me to have to tell him I know exactly what's going on when I'm in the absolute dark space?"
It didn't appear that he was a mad scientist. That had Mal breathing a small bit of relief, but he hadn't yet inspected his closets, so the tension wasn't going to die out any time soon for him. He was keeping his guard up. Using Simon as a clever cover story to cloak his own worry.