I almost missed NBC’s latest miniseries The Last Templar because I didn’t even realize it was scheduled until I checked a guide for Sunday night’s lineup. Since the Screen Actors Guild Awards on TNT indirectly preempted fresh episodes of most broadcast network series at 9pm EST, I decided to catch Oscar winner Mira Sorvino, The Unit‘s Scott Foley, and Alias alum Victor Garber on NBC instead.

Based on the debut bestseller of the same name by Raymond Khoury, The Last Templar follows the adventures of Dr. Tess Chaykin (Sorvino), a successful, spunky archaeologist and single parent of one daughter. She eventually becomes the informal partner of reluctant FBI agent Sean Daly (Foley) after four people on horseback raid a Manhattan museum opening for the Treasures of the Vatican exhibit and steal a number of priceless religious artifacts she and her deceased archaeologist father helped procure.

Working independently but colliding often, Tess and Sean gradually learn the horsemen were actually after one item: an ancient mechanical decoder used by the legendary Knights Templar to encrypt and decrypt secret written documents, including a message that supposedly indicates the location of invaluable lost treasure. Garber’s Monsignor de Angelis appears to be a sincere Vatican envoy who wants to help the FBI catch the thieves, even as a mysterious assassin hunts them down and murders them one by one.

Full of deliberately playful dialogue — Tess and Sean and his FBI partner tease one another nonstop — and predictable developments — who doesn’t guess the identity of the hitman’s boss after the individual’s second or third scene? — the first two hours of The Last Templar still manage to entertain, thanks to the decent chemistry between Sorvino and Foley and fairly exhilarating action sequences. The last include Tess chasing the museum thieves through the streets of Manhattan on horseback while her skimpy cocktail dress and expensive Manolo Blahniks struggle to stay on. Ridiculous, yes, but still fun to watch if you’re not expecting Masterpiece Theatre quality (and why would you?!).

Unfortunately, the second part of the miniseries kills all of the merriment — and momentum — when Tess and Sean head overseas to track down buried treasure in Turkey and then end up in Greece following a disaster at sea. Regardless of historical accuracy issues related to the 13th-century backstories, too many seemingly interminable and unnecessary scenes destroy the quick pacing established in the first part. And, don’t even get me started on how living legend Omar Sharif (Doctor Zhivago, Lawrence of Arabia), who plays nice old man Konstantine (the official description calls him a Greek savant, however), is exiled to the very end of the conclusion.

Despite a more-than-capable cast and a good start during The Last Templar‘s first two hours, the second part’s lack of speed to help viewers disregard the weak script and plot holes quickly sinks the miniseries, ruining any goodwill mustered while watching Part One. As a result, The Last Templar is ultimately like two movies: a passable original that goes on to severely disappoint in the sequel. Too bad.