... is what lead them to restrain her in the first place. Twice before they had rocked up at Catherine's doorstep, assuming she will be able to come on an outing with them, without regard for any plans she may have had previously, and for a 3rd time they are expecting her to drop everything to bend to their wishes, without returning the same favour. The kind thing to do would be to either consult Catherine first as to the best day for her to come with them, or else let her go on with whatever it was, and go on themselves.