Took far too long the parents to realize

They knew from the start that they took him from a spaceship, so they should’ve always had the sense that something might be off about him.

The mother saw him sleepwalking, trying to reach the ship while chanting stuff.

The father saw him chewing the fork, bending it thereby. They saw all the weird stuff under his bed. They had the incident where he broke the little girl’s hand.

And even when they found the blood covered shirt, the mother still insisted it wasn’t the boy. When the sheriff comes asking about the boy, the mother acts like an idiot.

Had they realized it sooner, the mother could have remembered that the ship cut him. Then he could have killed him.