Derek is so on edge with his senses so heightened that the movement of Reid's hand, subtle as it is, still catches Derek's eye. He can smell the blood and the pain and the healing flesh, and he swallows hard. His own knuckles are bloody, but the skin is already knitting back together where they split.

Sorry about your boyfriend. Derek has heard that before. Almost a year ago to a day, even. A shudder runs through him, grief and agony and the desire to shift, but he manages to keep it at bay. Barry hasn't disappeared. If he had, there would be no trace of him. That blood wouldn't have been on the brick. The stench of fear wouldn't have been there. Barry is here somewhere. He has to be.

"I'll come with you," Derek finally says, nodding a bit. He can smell Luke on Reid, on his clothes and his skin, and he has to breathe through his mouth. "Was there any sign of a struggle? There was-- I tracked Barry's scent and found blood. Not a lot of it, but enough."