Pratt realizes what Carlisle is looking for at the same time as Ami, but she gets to it before him. While Pratt already knew what Carlisle looked like under there, he does recognize that this is probably a shock for her - not to mention how hard he was trying to hide it.

The man had been through a lot already, from the situation with Kieran and now whatever had happened here. But burned forever in Pratt's memory was back in Hadriel, how he'd risked his life to save Pratt from Caedra. How he'd made sure that Pratt didn't wither away and avoid all human interaction forever, too traumatized by what he'd been through to think he was safe around people. A ticking time bomb that could go off at any moment.

Just like Carlisle feels now.

"And are you okay? What went wrong? Normally your limbs don't just.. pop off."