Paul is actually awake in the bed, having palmed the sleeping pill.
He gets up to explore the room and notices that the place seems to have been designed specifically to appeal to him.
A tiny hunter-seeker enters the room, and Paul freezes. Just like a T-Rex, the assassin's weapon won't be able to detect him if he doesn't move.
Mapes enters the room, and the hunter-seeker attacks. Paul's too quick, though. He grabs the thing in midair and smashes it against the door.
Paul tells Mapes to go to his father's men and tell them to search the premises for the operator.
First, Mapes needs to get the business of the water burden (read: life debt) out of the way. She knows there is a traitor in House Atreides. Although not specifically said, it seems she's going to sniff the traitor out.
Paul then goes to inform his mother, who is in the place Mapes called the "weirding room" (9.45).