Why not take it?
While he still hesitated, Mr.Vanstone and his daughter reached the top of the steps.

Once more, Magdalen looked round--looked with her resistless beauty, with her all-conquering smile.

She beckoned again; and again he followed her--up the steps, and over the threshold.

The door closed on them.
So, with a trifling gesture of invitation on one side, with a trifling act of compliance on the other: so--with no knowledge in his mind, with no thought in hers, of the secret still hidden under the journey to London--they took the way which led to that secret's discovery, through many a darker winding that was yet to come..