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. For a decade it remained the third and final book in the Mysterious Benedict Society series; however, a new adventure followed in 2019.
Plot summary
In the third installment of the Mysterious Benedict Society series, Reynie, Sticky, Kate, Constance, and various loved ones find themselves holed up in Mr. Benedict's house, which is teeming with security. The evil Mr. Curtain is at large and hunting for the Whisperer—now in Mr. Benedict's possession—so he can control minds from afar. 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. Of course, the rest of the Mysterious Benedict Society soon find themselves on his trail.
Soon, Reynie receives messages telling him a code number. He realizes it is a library code number, and Sticky tells them that that book's only copy is located in a library. They find Constance and an apparent clue to where the Whisperer is, but it turns out to be a trap. They are captured by Mr. Curtain. Kate makes several attempts to escape but does not prevail. Finally, their various loved ones come to the rescue, particularly Milligan, who fights McCracken, leader of Mr. Curtain's team of "Ten Men". Realizing that he is now bound for defeat, Mr. Curtain attempts suicide, but S.Q. prevents him out of love. In the end Mr. Curtain is arrested and sent to prison. Milligan retires, Constance is adopted by Mr. Benedict, and the families settle in the first and second floor of Mr. Benedict's house. (Or in Sticky's case, across the street.) The Whisperer was then later disabled by Mr. Benedict. His narcolepsy is later cured by Constance, thanks to her unusual gifts.