The scapula is a cheat. It hides a couple of different joints and protects the arm from harm when it bends outward -- it's also a notorious sticking place for knots and kinks, mostly because they can hide beneath the flat shell of bone. Castle's betting dollars to donuts that Beckett's got at least two or three knots right there. He moves his thumbs into position, pushing them around the outside curve of her shoulder blades --

"Oh yeah," he says, low and pleased, "the mother lode."