Angel of Vengeance: A Pendergast Novel.

"Angel of Vengeance: A Pendergast Novel" by Douglas Preston and Lincoln Child is the 22nd installment in the series featuring paranormal FBI investigator Aloysius Pendergast. In this book, Pendergast uses a dimensional portal to travel to an alternate version of 1880 New York City to protect his ward, Constance Greene's siblings from a sadistic doctor. However, Pendergast's evil twin brother, Diogenes, also follows them through the portal and forms an alliance with the doctor. The story is filled with contrivances and dialogue that some may find unrealistic, and the series as a whole has received mixed reviews. [Extracted from the article]