He blinked, suckling on her finger and tasting blood. Then he drew back, grasping her wrist with one hand and pulling it down so he could talk.

"I...didn't even think. I usually am very careful, please forgive me," he said, a tiny bit close to panic. And he started to disentangle himself. "I have some morning after pill in my lab. And I should draw some blood from you before you go."

Way to kill the mood.