“Mark Felt” is a drama about the man who, while second in command at the FBI in 1972 and 1973, simultaneously served as Deep Throat, an anonymous source to Bob Woodward of The Washington Post on the Watergate scandal that led to President Nixon’s resignation. Felt kept that secret until 2005 and died in 2008.

Liam Neeson is very good as Felt, who was sickened by Nixon replacing the late J. Edgar Hoover as FBI director with L. Patrick Gray, an outsider who was not part of FBI culture and more like a mole feeding information back to the White House about the Watergate investigation. The supporting cast of Brian d’Arcy James, Josh Lucas, Tony Goldwyn, and Ike Barinholtz play Felt’s underlings, but they all look so similar that it’s hard to tell who each character is.

Ironically for a Liam Neeson movie, there’s a missing child subplot. Felt’s teenage daughter had left home for parts unknown, a mystery that is played out in scenes with Neeson at home with Diane Lane, who is very good as Felt’s wife, Audrey, a tortured woman who drank too much. Unfortunately, we don’t get enough of Lane, who is always a pleasure to see on screen, because many of her scenes were cut for time — an edit that director, Peter Landesman, has apologized for.

Speaking of Landesman, who made the terrific 2015 Will Smith movie, “Concussion” (my review is here), this time he’s stuck with a very talky story that makes for a less-than-compelling movie. We see Felt talking with his FBI colleagues as they stand around a desk or move between offices, and as he occasionally slips out to discreet locations to spill the story to Woodward, but that’s not enough to get us invested in the story — particularly when we know how it will end.

“Mark Felt” wants to be a companion piece to “All The President’s Men.” Unfortunately, that classic covered much more than just the Deep Throat angle in a way that this can’t, relegating “Mark Felt” to not much more than a footnote, much like Felt himself.

I give “Mark Felt: The Man Who Brought Down The White House” a 4 out of 10, mostly for the performances of Neeson and Lane.