Title: Cathy's Key
Content:  Cathy’s Key (2008) is a novel continuing the storyline established in the first part of its series, Cathy's Book (2006). The story is written by Sean Stewart and Jordan Weisman, and illustrated by Cathy Briggs. As did its predecessor, the book takes the form of a 216-page journal written by the protagonist, Cathy Vickers. The book immediately picks up after book one of the series concludes, and follows Cathy in her quest to discover more about the mysterious and dangerous world of the immortals. Although many of the same characters (Emma, Cathy’s best friend, and Victor, Cathy’s boyfriend) are involved in the plot, there are also new characters introduced that complicate the storyline. For instance, a stranger met on a bus trip has developed by 
Title: Cathy's Book
Content:  Two sequels, Cathy's Key (2008) and Cathy's Ring (2009), have been published.
Title: Cathy's Key
Content:  Cathy’s Key follows the tradition established by its predecessor in presenting the story in a radically innovative way. Similar to a graphic novel, the text of the story is accompanied by hand-drawn images (created by illustrator Cathy Briggs), yet Cathy’s Key also contains a cache of objects that are related to the plot. For instance, the “evidence package” in Cathy’s Book contains artifacts such as a wedding invitation, a menu from a restaurant, various letters, a napkin, a death certificate, and four pieces of a ripped photo, among other items.
Title: Cathy's Key
Content:  end of the book into a major character, and new relatives such as Tsao, Victor’s father, appear in surprising and sometimes disturbing ways. At its most basic level, the plot involves Cathy attempting to navigate the treacherous world that the immortals inhabit while not imperiling herself or those she loves. Although high school graduation has come and passed and Cathy still doesn't have a job, she manages to keep busy by avoiding lovestruck immortals, trying to help her boyfriend discover the key to immortality, and in her free time delving into the mystery surrounding her father’s death. Although the story ends in another dramatic cliffhanger that leaves much to be resolved, Cathy’s saga continues in the third installation of the series, Cathy’s Ring (2010).
Title: Cathy Cassidy
Content:  Cathy Cassidy (born 13 June 1962) is an English author of young adult fiction. She was born in Coventry, Warwickshire. For a number of years she lived near New Galloway in Scotland where she started writing her novels, but has since returned to England, where she now lives on The Wirral. She has written 30 books and a few e-books as well. She has also been the agony aunt for Shout, a magazine for teenage girls, and she presently has a series of four books about Daizy Star for younger readers and a series of books for older readers called the Chocolate Box Girls.
Title: Cathy's Book
Content:  Cathy's Book: If Found Call (650) 266-8233 is a young adult novel with alternative reality game elements by Sean Stewart and Jordan Weisman, illustrated by Cathy Brigg. It was first published October 3, 2006 by Running Press. It includes an evidence packet filled with letters, phone numbers, pictures, and birth certificates, as well as doodles and notes written by Cathy in the page margins.
Title: Cathy Conheim
Content:  Cathy Conheim LCSW is a psychotherapist and the author of several children's books.
Title: Cathy (given name)
Content: Cathy Cassidy, British author and illustrator ; Cathy Crowe, Canadian nurse and social activist ; Cathy Peattie, Scottish Labour politician ; Cathy Priest, Canadian professional bodybuilder and figure competitor ; Cathy Wood, American serial killer 
Title: Cathy
Content: Dancing Through Life in a Pair of Broken Heels, written by Mickey Guisewite, Cathy Guisewite's sister (April 1994, ISBN: 0-553-37377-3) ; Lifestyles of the Trim & Healthy, written by Matthew Bennett (June 1994, ISBN: 0-9629502-9-7) ; Girl Food written by Barbara Albright & Cathy Guisewite (1997, ISBN: 0-8362-3173-2) ; The Complete Cathy: A Collection of Comics for Every Published for Sexy Superstar (April 2014 HarperCollins Publishers) The following books feature Cathy illustrations by Guisewite, but are not authored by her.
Title: Cathy Guisewite
Content: The Cathy Chronicles, ISBN: 0836211162, (1978) ; What Do You Mean, I Still Don't Have Equal Rights??!!, ISBN: 0836211588, (1980) ; I think I'm having a relationship with a blueberry pie!, ISBN: 0553013378, (1981) ; What's a Nice Single Girl Doing with a Double Bed??!, ISBN: 0553013165, (1981) ; Another Saturday Night of Wild and Reckless Abandon, ISBN: 0836212010, (1982) ; It Must Be Love, My Face Is Breaking Out, ISBN: 0836211839, (1982) ; Cathy's Valentine's Day Survival Book, How to Live through Another February 14, ISBN: 0836212045, (1982) ; How to Get Rich, Fall in Love, Lose Weight, and Solve all Your Problems by Saying "NO", ISBN: 0836219864, 

Question: Who is the author of Cathy's Key?
Answer: Sean Stewart.