Caitlyn was also curious as to what The Doctor was planning but she had heard such good things about his making up plans as he went about so trusted him to do so again.
Rose knew from experience that The Doctor could make up brilliant plans at the last moment so knew that she could trust him implacably. She let him do what he was planning not sure if she should follow or not, she took a hesitant step forward after he passed them. Making sure to stay behind him.