The Mysterious Benedict Society and the Prisoner's Dilemma is a 2009 children's novel written by Trenton Lee Stewart and illustrated by Diana Sudyka.

When a shady businessman shows up with false records claiming that he is Constance's father, Mr. Benedict is compelled to use the Whisperer to uncover her short past.

Distraught and confused after all is revealed that she is an orphan, Constance runs away, with the whole household after her—just the distraction Mr. Curtain and his men need to steal the Whisperer and set his evil plans into motion.

Booklist stated "Displaying much of the charm of the first book, this would make a fitting end to the series, but the Society's legion of fans probably wouldn't say no to more.

""[2] Common Sense Media wrote "But the story takes awhile to get going (the first 100 pages could have been condensed to 20)," and "A few more surprises and twists would have been welcome.