This is Rex, our fearless and learned seer. He can tell us midnighters apart from normal boring people, because we're the only people in focus unless he wears his big thick-ass glasses. He can also spot where the darklings have been, because they leave a sort of slime trail of focus behind them as they skibble across the frozen world at midnight. Basically, anything that's been affected by the secret hour catches Rex's eye. More importantly, he can read the Lore, which is the history of the secret hour as written by lots of seers in invisible seer ink over the centuries. There have been midnighters in Bixby for about 10,000 years, exploring the secret hour and kicking darkling ass. Unless Rex is making the whole thing up . . . (I mean, it's not like the rest of us can read that stuff.)