I need to get out of here before he catches on...

"Yes, the library! And, darn, look at that, I forgot my notes! Silly me!" Back away quickly, but not so quickly my complete lack of mammary support is given away, and...

"I'll see you in a little while, then!" That is one completely not-suspicious smile!

"Yep!" Out of the light, turn and walk very, very briskly away...