Disclaimer: I own nothing, and the story may not follow the episode exactly. Any mistakes are mine.
"I need to know I can depend on you Vin. Let me know when I can"
At the time that had seemed like the right thing to say. He wasn't shouting at Vin and he hadn't said anything that he thought was particularly hurtful. He just wanted Vin to stay and he wasn't above guilt tripping. Besides that was partly how he felt, Vin always seemed to be one step ahead of everyone else, always watching their backs and taking first watch, now Vin was distracted by Charlotte and Chris felt…vulnerable. A small part of him wanted to be happy for Vin, obviously he'd found someone who made him forget about the harsh realities of the life they lived. But the larger part of him wanted the seven of them to stay together. He'd turned his horse away from Vin and rode away, thinking that Vin would not be fully alert of their surroundings whilst his mind was distracted. He watched as Vin circled back and rode along the length of the wagon train, before cantering to the front and trailing ahead of the others.
At the time that had seemed like the right thing to say. But as he heard the gunshots and kicked his horse into a gallop towards the front the only thing he could think of was that if Vin was hurt, or worse, the last thing he'd said to the man was that he felt like he couldn't depend on him. He looked up in time to see Vin turn his back on O'Shea's men in order to sever the fuse and the dynamite. He'd smiled at that point. Knew I could count on you Vin. Then there'd been an explosion and he'd watched as Vin was thrown backwards down steep hill by the force, landing in a heap at the bottom with a bone jarring thud, a crumpled unmoving heap. Chris dismounted heart in his throat and raced towards Vin's prone figure. Another explosion assured him that Buck and JD had taken care of the powder-man hired by O'Shea. But it was a distant thought. He was entirely focused on the unconscious form at the bottom of the hill. He reached Vin a couple of seconds faster than Nathan and Vin was coming round as he got there.
He dropped to his knees behind him and pulled the sharpshooter so he was resting on his knees. "You alright?" Vin's head slumped to his chest and he replied "Most of me" voice laced with the pain he was trying to deny. The words hit home in Larabee's chest Vin was hurting. "Alright come on" He slipped his arms under Vins and pulled him to his feet in one swift motion. Not entirely prepared for the trackers legs to give out he was glad that Nathan was there too. By the time they reached the wagons Vin had shrugged them off and was walking stiffly on his own. Nathan tossed Vin's gun to him and both watched as he caught it, passing the little test. But then he bent in on himself, teeth gritted against some form of pain. "Sure you're alright?" asked the leader, concerned as normally stoic Vin showed pain. Vin seemed to notice this and straightened "Ah feel better than I look". This seemed to placate the concern in Chris and he set about getting the seven together to go after O'Shea. Pushing the apology that had been on the tip of his tongue to the back of his mind.
It hadn't been until they had reached Four Corners again that Vin had visibly shown any signs of pain. As they had left the wagon train, Chris had asked Vin if he was okay but he was not referring to physical injuries he was referring to Vin leaving Charlotte. Vin had said that Charlotte belonged here and all Larabee could think of was that he was grateful that Vin had decided to stay with them. Although he couldn't place when the tracker had slipped past his barriers, they had become like brothers, and he wasn't sure, after Sarah and Adam, that he would be able to cope with Vin leaving too. They'd made good timing and had reached the t own as night had begun to fall. Not taking time to rest as they did not want to be open to exposure with Mary and Billy in their group. Vin had separated after settling his horse in the livery and although he was usually quiet, the other six noticed his departure. Out of the six only Nathan noticed the arm protectively cradling his ribs. As the other left the livery Nathan went to look for Vin, checking the boarding house and not finding him he was on his way to check Vin's wagon when JD's shout echoed along the street.
"Nathan! Nathan! Something's wrong with Vin! Chris! Nathan! Somebody!"