NEW YORK (AP) — Lonny Price had just started editing his first documentary when a bunch of boxes showed up. What was in them would change everything.

The director was working on a movie about the making of Stephen Sondheim's 1981 ill-fated musical "Merrily We Roll Along," which closed after just 16 Broadway performances. Price had a unique perspective, having been one of the main stars in the ill-fated show.

While he was working on his film — "Best Worst Thing That Ever Could Have Happened ," which opened in New York last weekend and heads to Los Angeles before it shows in more cities in December — Price craved what he didn't have.

He remembered that 35 years ago, when he and his young cast were preparing for their Broadway opening, a film crew from ABC had captured their tryouts and rehearsals for their own aborted documentary.

Price wanted that footage. ABC said it was destroyed. He didn't believe it.

Price hired a specialist who finds lost footage. His forecast was grim: "He said, 'You have a nine percent chance of finding this.' Not even 10 — only a nine percent chance," said Price. "I said, 'I think it's there.'"

After years of filming, Price was two days deep into editing his documentary when 37 boxes of film canisters were delivered from a sprawling site in Connecticut. They contained the raw, behind-the-scenes footage from "Merrily We Roll Along" auditions and rehearsals.

"It was one of the best days of my lives," he recalled. Price might now have to stop and absorb the new footage, but he was happy. "It would have been a very different movie obviously if I hadn't found it."

The documentary is as much a look at how the original cast approached the show as what the show did to the cast. Price interviewed them all, including "Seinfeld" star Jason Alexander, to find out what happened after the musical closed.

Many had their theater dreams crushed and left the business, others struggled on. "We all turned out OK and I think we all feel OK," Price said. "I think there's a price you pay to hold onto your dreams and there's a price you pay to give them up."

For a movie that explores youthful idealism, getting that lost footage was crucial. Price had filmed some university students performing the musical to act as stand-ins, but getting his hands on the real first cast — including himself — was priceless.

"It was the Holy Grail," he said.