Sentinel always felt guilty about having to sedate his sister. But it had to be done. On the night of the party that was supposed to be going on, he and Jax had locked Jinx in her room and given her a sedative so that she wouldn't be able to get out and seek out the party. It wouldn't have ended well. He spent the rest of his time that night in his room, just to make sure that she didn't wake up and try to break the lock on her door. He didn't really sleep much that night, simply because he didn't feel tired at all. The next morning and most of the next day had been spent the way he normally spent his days. Doing what Jax wished of him and keeping an eye on his sister. Thankfully she only read and played chess for the day. Nothing dangerous.
That day, however, she'd asked to go to the market at the Trading Post. At first, his automatic answer had been no. He suggested other things she could do while staying at the lodge. But she had persisted. And even if Jinx was mentally unbalanced and he knew full well how dangerous she could be...she was still his little sister. So, eventually, he relented. But, of course, he would accompany her to make sure nothing went wrong.
Sentinel walked with his sister, only getting behind her when she'd skip ahead of him. He only casually looked over the items in the stalls, not really interested in anything. Finally, Jinx found one that interested her. He walked over then, standing by his sister but not saying anything.