“Hawaii Five-0” finished a successful first season Monday night with a plot that had more twists than Tantalus Drive, a breathless race to the credits and a body count that included two recurring characters.

But even all that was not enough to claim the hour, according to Nielsen ratings released yesterday by CBS.

In its 24th and final episode of the season, “Five-0” drew 10.4 million viewers to finish behind ABC’s “Castle,” which drew 12.9 million viewers. NBC’s “Law & Order: L.A.” finished third with 4.3 million viewers.

Nonetheless, it was still a remarkable season for “Five-0.”

When CBS aired first-run episodes, “Five-0” won its hour 13 times. It became the top-rated new show of the season.

It premiered in September to an audience of 14.2 million viewers, something that was only surpassed once: “Five-0” drew 19.3 million viewers when the network aired the show in a special Sunday time slot after the NFL’s AFC championship game.

One of the biggest challenges for the show was its own legacy. The original “Five-0” aired from 1968-1980 but has remained an iconic favorite among Hawaii residents — and that could have worked against the new version, said Walea Constantinau, commissioner for the Honolulu Film Office.

“The legacy can be like a gale-force wind against you if you don’t do it right,” she said. “The trick is to balance the old with the new. It is never easy, but that show is such a big show and had so much to live up to. And they met all expectations.”

For the whole season, “Five-0” had been a conversation starter wherever she went, Constantinau said.

“I can go just about anywhere in this town and someone will ask about ‘Five-0,’” she said. “They are excited to say they watch it all the time.”

Monday’s episode ended with a number of cliffhangers and the promise to continue the story line. But a second season won’t be official until today, when CBS announces its fall lineup.

It would be a felony plot twist worthy of the finale if that failed to happen. CBS began the season with only a 13-episode commitment to “Five-0” and finished with national and international syndication deals that will earn about $2.5 million per episode. Leslie Moonves, the network’s chief executive officer, earlier this month called “Five-0” a franchise worth billions of dollars.

Peter Lenkov, the show’s executive producer and the man behind the rebooted version of “Five-0,” recently told the Star-Advertiser that his writers are already working on scripts and that production would resume in July.

A second season won’t be easier, but the culture of the show will be familiar, even comfortable for all concerned, Lenkov said.

“We are a well-oiled machine now,” he said. “The writing staff knows who the characters are. They are familiar with their rhythms as actors. They know what works and what doesn’t. And the crew is a family.”

But for every success there is a failure, and yesterday that was the case for the other network drama that filmed in Hawaii this past season: ABC’s “Off the Map.” The drama about doctors working in a remote jungle clinic was canceled by the network.