Mara felt the floor tilt. "A boy? I have... another brother?"

Introduce a "skeleton in the closet" that one person knows, one suspects, and others are protected from. The tension comes from the looming threat of the truth coming out. 2. Map the Roles (The Burden of Identity)

Caleb stood there. He was wearing a suit that cost more than Mara’s car, his tie loosened just enough to suggest he’d been working, not worrying. His face cycled through shock, irritation, and finally, a smooth, practiced neutrality.