Character mistake: After cracking the clue of Silent Dogood letters, while leaving the shopping mall, Riley asks Ben and Abigail, "Who was the first to propose daylight saving time?". They reply "Benjamin Franklin". But, it was George Vernon Hudson in 1895.
Continuity mistake: When Ian looks down to the shadow cast by the "House of Pass and Stow", the shadow isn't anywhere near to where it was when Ben looked down, although not very much time could have elapsed.
Answer: He doesn't simply assume "Beneath Parkington Lane" means beneath the church: Parkington Lane is the name etched on the tomb hiding the entrance to the tunnels. When he saw it, he naturally deduced what he had to do.
Sereenie