the certainty the room hands him

Amid a calculus with no stable answer, exactly one operational fact resolves — and it is produced not by tradecraft but by Ennet House's informality. Because a torso (Johnette's) can lean "with suddenness into the office unexpectedly," through a door with no lock worth the name, Marathe "decided firmly against the snapping of any necks upon this visit." The demi-maison's loose, unguarded sociability defeats the assassin more reliably than any countermeasure: you cannot murder cleanly in a house where people appear without warning. The one certainty on the outcropping of his mind is a negative, and the halfway house authored it.