14
Sat at the Slytherin table in the Great hall, waiting for the sorting to begin, Tom let his gaze casually flit around the room. His year mates would assume that he was just having a look around, checking out whether there were any new staff (he'd already done that. New care of magical creatures teacher.) They wouldn't notice that he carefully checked the length of the Ravenclaw table, or if they did assume that he was just absent mindedly glancing. On his first sweep he missed her, and he had to force himself not to tense up, lest the girl sat next to him notice.
Then someone leant forwards, having been sat back to talk to someone further along the table, and the red hair swung forwards. She happened to glance up, and apparently absent mindedly looked over the other three tables. Her gaze rested on him briefly, and she nodded slightly. He tilted his head ever so slightly in response, then turned his full attention back to the conversation going on around him. That was the last item off of his checklist for the return to school, showing no external sign of his relief. Even if she was muggleborn, he didn't particularly want her to have died. A little too close to home. He vaguely wondered whether she had stayed at a friend's house. It was much more likely that Ravenclaws would understand, given the degree of halfblood and mudblood students in the house. Not like Slytherin, where there were only a few halfbloods, all of whom but himself lived their lives in the wizarding world.
And of those? None openly admitted to being halfblood. He had made it his business privately to be certain of everyone's blood status, and had carefully made it clear to everyone that he had no way of knowing his own lineage - yet every single member of his house was certain he was pureblood. And while he didn't believe it to be true, he saw no reason to correct them.