Thump thump thump...
Red's heart was amplified as his ears were directly pressed on top of the concrete floors. He could also hear Curl slowly approaching him like a cat who's about to sneak up on her owner. This made Red a bit conscious as to what Curl was about to do next.
What is she planning? Wait... does she know about my plan? Does she want to jump in on it? No, that's impossible. I've never told nor hinted anyone about it. A series of uncertain thoughts flashed through Red's mind as he fought the urge to turn around and gaze directly towards Curl's eyes. She wanted to catch her red-handed on what she's about to do but he didn't want to jeopardize his plan since he only had one chance at it. That's why, although he didn't know what's about to happen, he just remained in his sleeping position, hoping that Curl would go away.