Dink is a serious, thoughtful boy living in the small town of Green Lawn, Connecticut. He aspires to become a famous writer and is a massive fan of mystery novels. His love for reading equips him with investigative skills, making him eager to uncover the truth when his favorite author goes missing. He feels a strong sense of personal responsibility for the disappearance because he sent the invitation.

Josh is Dink’s loyal and slightly mischievous best friend who dreams of becoming an artist. Unlike his friends, he does not read mystery novels, which results in a more unfocused, highly suspicious approach to solving problems. He willingly takes risks during investigations, perfectly balancing his friends' methodical methods.

Ruth Rose is Dink’s next-door neighbor and an inquisitive, intelligent girl who loves reading. She approaches problems methodically and isn't afraid to speak her mind when pursuing clues. Her keen memory for details found in books provides critical direction when the investigation hits roadblocks.

Wallis Wallace is a renowned children's mystery author who lives in a castle in Maine called Moose Manor. Known for donating to animal conservation programs and loving the color green, the author maintains an air of mystery. Wallace's disappearance immediately before the Green Lawn book signing sparks the central investigation.

Mr. Paskey owns the Book Nook, the local bookstore hosting the signing event. He is a nervous, easily rattled man who sweats profusely when things go wrong. He provides the children with the missing author's itinerary, giving them their first real lead.

Maureen is a sarcastic, cheerful cab driver with bright blue eyes. She is a messy eater who enjoys doing crossword puzzles during her breaks. She confirms picking up the author from the airport, offering vital clues about the passenger's peculiar behavior.

Mr. Linkletter is a sad-looking hotel clerk with a mustache who firmly believes in following the rules. He acts as an obstacle for the investigating children by refusing to divulge guest information. His strict adherence to protocol makes him seem suspicious to the young detectives.

Olivia, also known as Livvy, is a hardworking maid at the Shangri-la Hotel and a mother of two. She provides crucial inside information about the hotel rooms that the front desk refuses to share. Her younger sister is a big fan of the missing author's books.

Officer Fallon is the local Green Lawn police officer. He dismisses the children's kidnapping theories as highly unlikely, suggesting a simple missed flight instead. He represents the safe, secure environment of the small town.

Dink's mother lives with him in Green Lawn. She is kept in the dark about the children's detective work because they know she would not approve of their investigation.

Jimmy is a young boy from Green Lawn who attends the scheduled book signing. He accompanies his grandfather on a trip to the local diner.

Tommy is a local boy attending the scheduled book signing. He is the first person to confirm to the arriving children that the author has not yet appeared.

Freddie is a man wearing a red cap who works at the hotel. He helpfully provides the children with the home address of the floor maid so they can continue their search.