WASHINGTON -- Author Katherine Marsh grew up outside New York City. To her, Grand Central Station's whispering gallery is "one of the coolest places in New York." If you talk really softly into a column there, your friend at another column across the room can hear you.

"What would happen," Ms. Marsh wondered, "if you whispered there and someone else answered, and no one was there?"

That's the question she sets out to answer in her books "The Night Tourist" and "The Twilight Prisoner." The adventure stories are about a 14-year-old boy named Jack and his ghost friend, Euri.

Ms. Marsh graduated from Yale University as an English major. She began writing children's books in the mornings, before work, about seven years ago, when she was an editor at a political magazine in Washington.

"I have always had this interest in writing fiction," she says. "I have a lot of memories and emotions around being a kid." She especially remembers having "a really tough year" when she was 14, when her parents divorced.

In her books, Ms. Marsh writes about things she loves and things that intrigue her: Greek mythology, New York City and the possibility of bringing someone you love back to life. Her grandmother died a couple of years before she began writing the first book. "I really missed her a lot, and it got me thinking about the world of the dead," she says. "I sort of wanted to commune with her spirit."

Ms. Marsh began "The Night Tourist" thinking that Euri was a time traveler, not a ghost. But that didn't quite work. "A lot of writing is this instinctual, gut feeling, and you know when something's off," she says. She wrote the ending of "The Night Tourist" a couple of times and cried when she couldn't let one of her characters live.

Ms. Marsh's books deal with some heavy issues, including death and impossible love. She often invokes the myth of Orpheus, who tried to rescue his wife, Eurydice, from death but failed when he disobeyed the gods by turning around to look at her. But the books are also fun, and you'll learn a lot of cool facts about New York City.

Ms. Marsh's advice to young authors: "Read!" Read whatever interests you and draws you into a story, she says. Think about "the rhythms of language," and then "try your hand at it, and try to imitate some of the people you like best." Keeping a journal or writing e-mails are also good ways to practice your writing, she notes.

"Island of the Blue Dolphins" by Scott O'Dell and "Walk Two Moons" by Sharon Creech are a couple of Ms. Marsh's favorite children's books.

These days, she is working full time on more children's books from her home in Washington, where she lives with her husband and her young son, Alek. She hopes to write a third one about Jack and Euri. "The Night Tourist" is set to be made into a movie. There's no release date yet, though, so you have plenty of time to read the book before you see the film.

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