Dalton Trumbo was the most famous of the Hollywood Ten, the screenwriters blacklisted after the House Un-American Activities Committee branded them as Communists in 1947. But from an aesthetic rather than a political perspective the really important thing about him was that he was a master craftsman. As such he would never have countenanced a script as conventional and heavy-handed as the blandly chronological one John McNamara has constructed about him—which has been directed with an equal lack of imagination by Jay Roach. “Trumbo” has the feel of a decent cable movie: though it’s watchable, you leave it certain that the man, and the situation he was forced into, are deserving of much better treatment. And you’ll probably also conclude that the lead performance by Bryan Cranston is too theatrical a turn, one that would be more suitable on the stage or the tube, where distancing would mitigate its broadness of technique.

Nonetheless, though “Trumbo” may be a workmanlike job rather than a truly revealing portrait, the story remains a compelling one. Trumbo is introduced as the supremely successful screenwriter of such films as “A Guy Named Joe” (1943), happily married to loving—and tolerant—wife Cleo (Diane Lane), with whom he has a young son and two daughters, and the recent signer of a lucrative contract with MGM. He’s also among a group of activists espousing Communist ideals—a group supported by some actors, including Edward G. Robinson (Michael Stuhlbarg), but castigated by such anti-Communist stalwarts as John Wayne (David James Elliott) and columnist Hedda Hopper (Helen Mirren).

It’s the activism that brings Trumbo and his leftist colleagues to the attention of the House Un-American Activities Committee chaired by J. Parnell Thomas (James DuMont). He encourages them all to follow his lead and refuse to answer the committee’s questions, which brings contempt charges and, after a series of legal maneuverings, jail time—eleven months for Trumbo himself.

Upon emerging from prison, Trumbo finds himself blacklisted by the studios (a circumstance stage-managed by Hopper, who’s portrayed here as a central figure in his marginalization) and forced to write scripts at bargain-basement rates for schlock moviemakers like the King brothers, gregarious Frank and the more subdued Hymie (John Goodman and Stephen Root)—for whom he nonetheless wrote a screenplay(“The Brave One”) which nabbed him an Academy Award in 1956. Later he’s recruited by the likes of producer Buddy Ross (Roger Bart)—who, we later learn, gave names to HUAC (as did Robinson)—to doctor scripts under a pseudonym, or the name of an actual person who served as a front for the process. Trumbo’s incredible productivity put a strain on his relationship with his friends (one of whom—Ian McLellan Hunter, played by Alan Tudyk, actually won an Oscar for the screenplay of “Roman Holiday,” which Trumbo actually penned)—and his family, particularly his daughter Niki (Elle Fanning) and son Chris (Mattie Liptak), whom he enlists, all too demandingly, as his couriers in the script trade.

Trumbo’s aim—to break the blacklist—came true in the late fifties, when he was approached by two Hollywood bigwigs to work on their projects—Kirk Douglas (Dean O’Gorman) on “Spartacus” and Otto Preminger (Christian Berkel) on “Exodus,” both released in 1960. McNamara dances around the controversy over which of the two actually “broke” the blacklist (Preminger announced his intention to credit Trumbo first, but “Spartacus” came out, with the onscreen credit, first). But the film gets a lift from the one-upmanship between the two titans, and Trumbo’s playing them off against one another.

The Douglas-Preminger material, incidentally, isn’t the only place where McNamara and Roach massage the historical record for dramatic effect. Trumbo couldn’t have bumped into his nemesis Thomas in prison, as shown here—though the congressman was convicted of fraud, he wasn’t sent to the same facility as Trumbo (though a couple of the other blacklisted writers were). The King brothers, as broadly—and delightfully—played as they are, were real people, but Arlen Hird (Louis C.K.), Trumbo’s fellow writer and constant sounding-board, isn’t: he’s a composite figure drawn from no fewer than five other blacklisted scribes. Ross is a composite as well, a blend of Dore Schary and Walter Wanger.

But such alterations are to be expected in docu-dramas, and they’re hardly fatal to the point of the picture—the needless human damage done by reckless people posing as patriotic champions in times of political unease, and of weak-kneed souls who collaborate with them, a lesson that deserves to be remembered as much today as in the 1950s. The problem with “Trumbo” is quite simply that it opts constantly for the obvious—in Trumbo’s self-righteous speechifying (at one point he dresses down Wayne), in the coda that italicizes the same principles, and even in Theodore Shapiro’s heavy-handed score, which overemphasizes every emotional moment.

And if the film isn’t all that good, it’s still enjoyable—not just because Cranston works so hard (or perhaps too hard) to bring Trumbo to vivid life, and because the crafts crew (production designer Mark Ricker, art director Jesse Rosenthal, costumer Daniel Orlandi) work equally hard on the (sometimes lovingly exaggerated) period ambience, which cinematographer Jim Denault goes to great lengths to convey in vibrant widescreen images, but also because it’s simply fun to see people like Stuhlbarg, Elliott, Mirren, O’Gorman and Berkel do their impressions of famous folk, and Tudyk, Goodman and Bart theirs of less well-known ones. (Others like Lane, unfortunately, are pretty much wasted, and Louis C.K. is just playing himself.) There’s no more subtlety to any of their performances than there is to Cranston’s, or to the picture as a whole. But the tale itself is fascinating, and in “Trumbo” the story is the thing, and even an imperfect telling of it is better than none.