NEW YORK (CBSNewYork/AP) — What do you get when you combine Stephen Sondheim and dinosaurs? No, not “Jurassic Park: The Musical.”

Those lucky enough to attend a gala benefit on Monday night at the American Museum of Natural History will find out. Sondheim, a legendary puzzle maker besides being a cherished songwriter, has created his first ever treasure hunt to be held among the dinosaur bones.

The event — a sort of “Night at the Museum” meets “National Treasure” — is to celebrate the 20th anniversary of Friends In Deed, a nonprofit crisis center based in Soho that provides emotional and spiritual support for anyone diagnosed with life-threatening physical illnesses.

Cynthia O’Neal, co-founder and President of Friends In Deed, believes that the fact Sondheim is doing a hunt for their fundraiser is “thrilling.”

“Stephen Sondheim volunteered several weeks ago to do one of his famous treasure hunts for us as a fundraiser. Which is thrilling because he doesn’t do them very often and they’re really an iconic New York thing,” she told 1010 WINS.

“I’m just excited to see what he’s going to do,” says Raul Esparza, the Tony Award-nominated actor and singer who has appeared in such Sondheim musicals as “Sunday in the Park With George” and “Company.”

Esparza will be one of several hundred guests split into teams who then follow Sondheim’s clues as they wander the museum’s two massive dinosaur halls, where the T-rex stands. Each team will get a different first clue to minimize crowding.

“I expect the clues to be — maybe not always, but sometimes — very cryptic,” says actor Anthony Rapp, Friends In Deed board member and “Rent” original cast member. “But he probably has to scale the difficulty to some degree because it can’t take all night.”

Then, after a winner emerges, he and Barbara Cook will sing for the rest of the guests during a sit-down dinner in the museum’s planetarium. Several hundred attendees have signed up, including Bravo’s Andy Cohen, director-writer Nora Ephron and news anchor Diane Sawyer.

Seats to the event, called “A Little Jurassic Treasure Hunt” and hosted by Sarah Jessica Parker and Matthew Broderick, cost $1,500. The goal is to have some 300 guests and the organization says there are still tickets available.

“We are a relatively small organization in many ways but it just seemed important to do something pretty special for the 20th anniversary,” says Rapp, who was aided by the group when his mother was ill.

As his intricate lyrics suggest, 81-year-old Sondheim is a crossword puzzle fan and word game aficionado who in the past has sent clumps of friends on private scavenger hunts across the city and his home in Connecticut. He and actor Tony Perkins hosted their first Halloween hunt in 1968.

“I thought that was maybe the coolest thing I’d ever heard: New Yorkers following a Stephen Sondheim puzzle around. So I can’t believe that he agreed to create another one,” says Esparza.

Friends In Deed was co-founded in 1991 by film director and producer Mike Nichols and actress Cynthia O’Neal, who serves as its president. Its free programs help those who are battling AIDS, cancer and other diseases or dealing with bereavement, as well as family, friends and caregivers of those who are ailing.

O’Neal told 1010 WINS why she thought her organization has been so successful over the past 20 years.

“The things that we deal with are things that there isn’t anybody that isn’t going to have to deal with them in their lives — I don’t know anybody that isn’t going to have to deal loss at some point, illness at some point, care giving.  I mean, these are the most universal and most difficult things to deal with that human beings have,” she said.

Sondheim, who has been associated with Friends In Deed for several years, offered to lend his puzzle skills for the 20th anniversary celebration over dinner last spring with O’Neal, an old friend.

“Because I don’t like to ask things of my friends, I had never asked Steve if he would do it, but it was certainly a thought that I harbored,” says O’Neal, who once participated in a Sondheim treasure hunt. “I don’t know exactly how, but the subject came up and he said, `You know, I’d love to do one for you.'”

O’Neal has no idea what Sondheim is planning and that’s fine by her. “There are those who do, but I don’t because I want to do it,” she says. “I don’t know what’s going on in that brilliant little mind.”

Though he’s never been on a Sondheim-designed treasure hunt, Esparza has heard stories about previous ones. In one, contestants showed up at a brownstone and were served tea and cake. A clue appeared at the bottom of the tea cup. It read: “You can’t have your cake and eat it, too.”

It turned out that when all the team’s cake slices were rearranged, the icing would reveal a map of the next rendezvous. If the cake pieces had been devoured before the clue was discovered, though, the team was doomed.

For Esparza, there’s a lesson there that he intends to remember at the gala: “Don’t eat anything until you’re told you absolutely can.”

(TM and Copyright 2011 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2011 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)

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