Hertz is a Ten Man introduced in the third book, The Mysterious Benedict Society and The Prisoner's Dilemma. He was doing a crossword puzzle and escorted the Mysterious Benedict Society to Mr. Curtain in Third Island Prison.
Hertz is described as being a slight, swarthy man in a dapper seersucker suit. Hertz is the Ten Man that Kate had injured earlier in the book, during the raid on Mr. Benedict's home. He was hit in the head with her flashlight. Soon after, he fought a battle with Ms. Plugg and almost lost, eventually gaining the upper hand by putting his hankerchief over her nose.
McCracken described Hertz as afraid to touch the Whisperer, and Mr. Curtain replied that he had been chosen to help move the invention for this particular reason. To avoid any unnecessary pawing.
Hertz was dispatched along with rest of the Ten Men (not including Crawlings) to go to the gate of Third Island Prison, and intercept Mr. Rubicund. During the battle, he fought Rhonda Kazembee (black van) and Number Two (ersatz ambulance). He used his tie to grasp at doorhandles, but was repeatedly thwarted. His briefcase was said to have fallen open on the ground, but the two young women were not letting him get at it. The most he could do was to kick it out of harm's way. Eventually, the Ten Man was over powered, when chasing the ambulance containing Number Two. She stopped aburptly and he charged into it, knocking himself unconcious. He was presumably taken into custody along with McCracken, Sharpe, Garrotte, and Crawlings and two other Ten Men.