Thursday night - time to roll out the networks' big guns, literally and literarily.

ABC opens with Last Resort, perhaps the most ambitious and expensive-looking new series of the season, and a program whose mature and violent content seems ill-suited to the 8 p.m. slot.

The captain (Andre Braugher) and crew of a dreadnought ballistic Navy sub get an authenticated missile launch code. When both Braugher and his commanding officer (Underworld's Scott Speedman) have qualms about heaving nuclear warheads at Pakistan, their sub is targeted for destruction.

Their crisis is set against upheaval in Washington, where the president is facing an impeachment vote and members of the Joint Chiefs of Staff are resigning in protest over the (unseen) president's (unstated) policies.

Hunted by his own country, Braugher finds sanctuary for his sub and its 150 (but decreasing rapidly) crewmen and women on the lush if generic tropical island of Sainte Marina.

Last Resort has one of the biggest ensembles in prime-time memory, including the ship's lieutenant and admiral's daughter (Anna Paquin look-alike Daisy Betts), the subversive chief (The Unit's Robert Patrick), and a mysterious and deadly Navy SEAL stowaway (Daniel Lissing).

The heterogenous but generally dusky natives are also restless, particularly Sainte Marina's nefarious bossman (Sahr Ngaujah) and its Tiki-bar owner (Dichen Lachman of Dollhouse). There's also a French scientist (Camille de Pazzis) manning a fortuitously state-of-the-art NATO monitoring and communications station.

Back on the home front, you have your standard hard-charging, tough-talking, lingerie-modeling military industrial lobbyist (Autumn Resser) pulling strings like a hyper harpist.

And Speedman's wife (Jessy Schram of Falling Skies) is having her uxorial loyalty systematically undermined by devious intelligence operatives. How high does this conspiracy go?

Last Resort is going to need that rich blend of characters and plots. The pilot is sensational - a suspenseful, cinema-quality grabber. But once it lands on Sainte Marina, the sub becomes a large prop floating in the harbor and you're left with a battle zone Gilligan's Island.

Though smaller in scale, CBS's Elementary (10 p.m.) is daring in its own right, the latest iteration of Conan Doyle's immortal detective.

How popular is Sherlock Holmes? This intriguing new series isn't even the only contemporization of the deerstalker currently on television. PBS's Masterpiece Mystery! has a marvelous offering of his cases set in modern-day London. In fact, Benedict Cumberbatch deserved to win an Emmy this week as Masterpiece's Sherlock, but was jobbed by a hillbilly Kevin Costner.

The latest and thus far most tattooed Sherlock is CBS's Jonny Lee Miller (Eli Stone), exiled to Manhattan by his rich daddy after problems with addiction. But Sherlock, like Charlie Sheen, has a self-directed approach to rehab. To stave off his itchiest trigger, ennui, he will consult on murder cases with the NYPD - specifically Capt. Gregson (Aidan Quinn) - much as he did with Scotland Yard.

His constant companion (she's supposed to monitor him to make sure he stays sober) and chauffeur is Dr. Joan Watson (Lucy Liu of Southland).

It's hard to deal with the eccentric Holmes, who has curiously little regard for the people around him, considering how keenly observant and attentive to detail he is.

Despite his bad-boy appearance, Miller's Holmes maintains vestiges of an old-fashioned manner, particularly his diction. "Consider every wretched hive of depravity and murder in this city my place of business," he cautions Watson.

Those anachronistic touches add to the show's pleasure, seeing drawing-room-mystery conventions play out in the cellphone era.

The New York settings are picturesque, although the geography, as it was on Law & Order, is a little addled. The idea of a potter's field taking up real estate at 86th and Third is ludicrous.

Stylishly directed, Elementary is one loaded show, including its wonderful, well-matched leads. But its success will be singularly dependent on its writing. For reasons that should be pretty evident, Sherlock.