What roles do suspense and secrets play in Chapters 22 to 24?

In Chapters 22 to 24, there are quite a few secrets and suspenseful moments. We still don't know what Silas is looking for, but we are given the impression that it is priceless. Also, Sister Sandrine obviously has a secret mission to carry out. Meanwhile, Langdon is revealing to Sophie the secrets of the Priory of Sion, which he thinks Jacques was a member of.