HARMON HOPES TO RESCUE NCIS!

Rolls up sleeves to get back to work

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NCIS alum Mark Harmon is all aboard for a full-time return to the show in an attempt to save the ratings-challenged series from sinking.

Once the most watched show on TV, it has plunged to number 10, which insiders say has sent execs into crisis mode.

"NCIS has sunk in the ratings for the first time and people are nervous and seeing that as a bad omen of things to come," spills a source.

But the 73-year-old star, whose career has been defined by the series, believes he can save the military action drama from going down, says an insider.