A/N: 500-word drabble for Writing Challenge #9, "Suspicion."
Bellatrix first notices that something is off when Andromeda misses curfew, climbing through the portrait hole twenty-seven minutes late, eyes wild and face flushed from running. It isn't like Andie to be so careless; when she misses curfew, she does so intentionally, and she carefully orchestrates her movements so she won't get caught.
After that, Bellatrix watches. She sees the way Andromeda borrows the breadbasket from the Hufflepuff table and lingers there. She sees Andie's swollen lips and untidy hair, the new smile – too wide, too uncontrolled to belong to Andromeda – that bursts forth senselessly, at random times.
Bellatrix asks, but Andromeda lies, blaming the weather or grades or Quidditch for her joy. Bella can tell when Andie's lying, but she doesn't press. She's been doing a lot of lying herself, lately.
It doesn't take long to figure out who Andie's new smile belongs to. Edmund Macmillan. He's too self-righteous for Bellatrix to care much for him, but she can see why Andie might. Macmillan is good-looking, with thick blond hair and deep brown eyes; he's intelligent, one of the first in his class; and most importantly, he's from a good family. There isn't a Mudblood or a Squib in the Macmillan family tree for eight generations – Bellatrix knows, she's checked.
Macmillan is a Hufflepuff, true, but once you're out of Hogwarts, Houses really don't matter much. Slytherin house loyalty is just a mask for pureblood loyalty, after all, and Macmillan is a pureblood.
The only problem with Macmillan is the filth he hangs around with. Maybe he can't help it – being in Hufflepuff means he's forced to share quarters with Mudbloods and blood traitors – but Bellatrix doubts it. She watches him, and it's clear that his best friend is a Mudblood, Ted Tonks.
This must be why Andie hasn't told her.
But Bellatrix watches, and sees the way Andie carefully ignores Tonks. She only talks to Macmillan when the Mudblood is out of the way. Bellatrix approves, and trusts that Andromeda will be able to cure Macmillan of his unfortunate friendship.
That summer, Macmillan's eagle owl taps on Andie's window late at night, and the black and yellow Hufflepuff tie hidden in the bottom of her school trunk can only belong to him. Bellatrix is busy hiding her own secrets from Andromeda – the shields in her head and the mark on her arm and the blood on her robes – but Andromeda is too caught up in her own romance to watch Bellatrix.
Andromeda keeps her secret for over a year. Bella doesn't remember much about finding out – screaming and shouting and a frightening rage filling her veins, blinding her and making her destroy everything Andie left behind.
Days later, when Bellatrix comes back to herself, she laughs.
She should have known. It isn't like Andie to be so careless – when she misses curfew, she does so intentionally, and when she falls in love with a Mudblood, she makes sure her Death Eater sister thinks it's Edmund Macmillan instead.