Before I take a few days off, I strongly urge KERA readers/listeners/viewers to take the time to see the Tim Burton adaptation of Sweeney Todd — it is what the film critics have declared: bloody marvelous.

“Edward Scissorhands grows up,” said my wife, Sara, when the film was over. “And decides to murder everyone in Bleak House,” I added.

Few critics have noticed, however, what makes Sweeney so unusual as a musical comedy, except in the most general terms (the NYTimes’ A. O. Scott came closest): It’s the only musical comedy that is genuinely terrifying. Terror was not in the musical’s vocabulary until Stephen Sondheim came along. Sweeney is not terrifying in a cheap, horrorshow manner with the boogie man playing “gotcha!” and leaping out at you, although there is, of course, plenty of Grand Guignol, splatterific bloodshed in Sweeney.

No, it’s terrifying because it’s an appalling world: One of the bits left out of the film version is a brief scene in which Anthony, the young sailor, learns why the birds sold by a street vendor are always singing. (Joanna, the young woman he loves, has already been linked to singing birds, so the revelation has a particular weight.) They’re blind, he’s told. The vendor takes a hot needle and blinds them — ensuring that they’ll always sing because they don’t know where they are, so they always are sending out the only signal they can. This is a world, as A. O. Scott writes, without justice. It’s also a world, as he didn’t write, without mercy. Sweeney tries to build an order, assert a form of justice — and only heaps on more tragedy, more bloodshed. Todd, after all, is the German word for “dead.”

Sweeney Todd is Sondheim’s masterpiece, and although I have quibbles about the film version (where is the shrieking, workshop steam whistle?), my only serious criticism is that Johnny Depp plays Sweeney as more or less berserk from the moment he lands back in London. There’s really nowhere for his Sweeney to go — except with darker scowls and crazier, razor-swordplay. The great pivot point when Sweeney is foiled in his revenge and leaps at murdering anyone out of raging frustration (“There, sir! You sir! Come and have a shave!”) doesn’t have nearly the boiling fury and terror it should: Sweeney slips from skulking revenger to insane nihilist, a hack-and-slash serial killer.

If you haven’t seen it, book/daddy cannot recommend highly enough the DVD of the George Hearn-Angela Lansbury stage version. It’s not that the stage version is better; in fact, an appealing aspect of the Burton film is that it’s so strikingly different, one can easily enjoy both.

But on this point, in this scene, Hearn is truly awesome — pathetic and dangerous and physically scary. I saw the stage production, and you actuallly wondered if he might, in a fit of unwilling audience participation, wade into the seats, killing theatergoers. He could have — he was that dominating with that big bellowing voice.

The scene still brings me a chill whenever I watch the DVD. One sign of Sondheim’s genius: No other musical has anything even approaching such a moment.