Nicholas Jacobs had been watching Clara and Celine as closely as everyone else ever since the kidnappers came back and threatened to take them again. When he saw Clara sneak out into the restroom with nobody following her, he decided to take it upon himself to do it. Clara did not trust him after what he did, but he did not care. It was better to be safe than sorry. Clara could yell at him if that's what she wanted. He deserves it, after all.
He pretended to make a phone call, hiding near the men’s restroom doors. When he saw two uniformed hotel staff come out of the women’s restroom with a hotel trolley, the kind used to carry all the sheets and linens from rooms that have been emptied and he grew suspicious. These men didn’t look like the regular hotel staff. They looked more buff and were suspiciously gruff-looking, covered with all those tattoos. So when they left, he checked inside the restroom, and sure enough, Clara was gone.
