He's getting the syringe into the disposal container when he sees Tosh's face go white. Getting hit with a reminder of a trauma is something he's very familiar with; Ianto had to help him through plenty of that. He hurries to get that dropped in and put the vial out of sight in the bag, then he goes up to the sofa, ready to pull her in. "Hey, hey, it's all right. Look at us, okay?"