‘Hack’ goes over gritty territory

Since being banished from the police force in disgrace, Philadelphia cabdriver Mike Olshansky has found a new calling: helping untangle the troubled lives of some of his fares. But in tonight’s absorbing installment of “Hack,” it’s Olshansky who needs the help, and a passenger with revenge on his mind is the reason why (9 p.m. CBS).

Of course, when it comes to ratings, the series could use some help of its own. “Hack,” starring David Morse as the cabby, has struggled a bit since debuting last fall. Some viewers seemingly have difficulty getting their arms around a flawed protagonist who, while aware of the line separating right from wrong, doesn’t mind striding right over it if need be. And his former partner, Marcellus Washington (Andre Braugher), is cut from the same ragged cloth.

Yet it’s the moral ambiguities that make the series such an unusual treat, and tonight’s episode is a riveting example. Olshansky is taken hostage by John Scanlon (Gary Cole), whose brother Jimmy (Chad Lowe) is imprisoned and counting down the final hours before his execution for killing a cop. In flashbacks, we see the disturbing circumstances surrounding the slaying, and Olshansky’s role in how it played out.

Now John, who has his prey locked up in a makeshift cell, wants to force Olshansky to go through a countdown of his own, with John serving as executioner at the very moment Jimmy is put to death. The episode, directed by Alex Zakrzewski from a script by Brad Buckner and Eugenie Ross-Leming, ratchets up the tension as Olshansky is allowed a last call to his estranged wife, who sets in motion a rescue attempt as Jimmy is readied for his lethal injection.

In a TV landscape where complex issues are resolved with a sterile, color-coded neatness, this episode ends bathed in shades of gray.