Sara didn't see the shocked expression on Tracey's face, she was to focused on making it look like she was doing something that might be perceived as work. She didn't want to stop, it was getting to feel so good, but she had to, who knows what McGonagall would have done with the information that Sara, the heir to the Moon family name, was a lesbian. She knew that old women like that couldn't help but to gossip.
Resisting the urge to roll her eyes as her professor criticized the work, Sara bit her cheek to retorting with a sarcastic remark. She didn't feel like getting a long lecture about how she should respect authority and her elders, she was to distracted by her arousal that Tracey had caused and shifted on her feet impatiently for McGonagall to let them go.
Finally, they were released from their detention, but Sara didn't say a word until McGonagall was out of sight. Then, after making sure the hall was empty, she turned to Tracey and spoke in a low voice. "I didn't want McGonagall to catch us, who knows what that hag would do with that information." She didn't apologize.
SHifting again on her feet, she leaned in slightly to Tracey, "But I'd like to...continue, somewhere, if you wanted."