THE BABY-SITTERS CLUB #13: MARY ANNE'S BAD LUCK MYSTERY is Cynthia's debut graphic novel. 

Description: 
Mary Anne should never have thrown away that chain letter she got in the mail. Ever since she did, bad things have been happening to everyone in the Baby-sitters Club. With Halloween coming up, Mary Anne's even more worried -- what kind of spooky thing will happen next?

Then Mary Anne finds a new note in her mailbox: Wear this bad-luck charm, it says. OR ELSE. Mary Anne has to follow the note's instructions. But who sent the charm? And why did they send it to Mary Anne?
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The BSC might never see an end to their bad luck if they don't solve this mystery soon!

Available via:
Scholastic
Indiebound
Books A Million
Barnes & Noble
Target

Take a look at the process of adapting the graphic novel from the original book: