On the Fifth Day by A.J. Hartley

An interesting and exciting book never heard of this author a most entertaining read, i empathised with all the characters.

From Goodreads - The death of a priest is met with suspicion by his brother Thomas, who knows that his sibling died while researching Christian symbols. But Thomas and curator Deborah Miller aren't alone in retracing the priest's final steps. They're followed by fanatics desperate to hide the secret stumbled upon by Thomas's brother-and willing to kill to keep it buried forever.