WARNING: SPOILERS

The last great mystery in the great career of Sherlock Holmes results from his own senescence—his inability to remember his last great mystery. That's both smart and sad. In moments when Holmes (Ian McKellen) looks slack-jawed and dumbfounded, I kept thinking of Ophelia’s line in “Hamlet”: Oh, what a noble mind is here o’erthrown!

Even smarter is the casting. You know how people used to say they’d pay to hear John Houseman read the phone book? I think I’d pay to hear Ian McKellen say one word. In “Mr. Holmes” that word is “Portsmouth,” the coastal village to which his housekeeper, Mrs. Munro (Laura Linney, doing Bri’ish), is thinking of moving with her son, Roger. Holmes doesn’t want them to go, so he dismisses it out of hand. McKellen can convey so much with a glance or a tone, and he says “Portsmouth” as if it were a small, sad place that’s fine enough for, you know, them, but not really for people like you and me. I got such joy from his reading of that one word. 

Good casting as well for Roger, a whipsmart boy from working-class parents who idolizes Holmes and his smarts. “Are you going to do the thing?” he says early on, and we know immediately what he means: how Holmes can extract a person’s story from seemingly inconsequential details. It’s Holmes’ superpower. In this story, Roger is essentially Holmes’ Watson, and Milo Parker, who looks like a dark-haired cousin to Thomas Brodie-Sangster (“Love, Actually,” “Game of Thrones”), is perfect for the role: curious with Holmes but not above being bratty with his mum.

It’s 1947, and Holmes, 93 and living on the coast of England, is trying to recall and write about the case that ended his career 35 years earlier. He’s trying to set the record straight—a record that his companion, the long-departed Dr. John Watson, bent out of shape with heroics and deerstalker caps. Except Holmes doesn’t remember how that case ended. He doesn’t remember a lot of things, so he’s forever writing notes to himself on his French cuffs.

The movie is split into three parts:

1. A recent trip to post-war Japan to purchase “prickly ash,” which is supposed to help him with his fading memory.
2. Present day, 1947, in which Roger helps Holmes with his apiary, while Holmes tries to write the story of his last case.
3. That last case.

The present-day story is the best, Japan the weakest. Holmes’ reason for going to Japan is far-fetched, and the mystery behind his host there, Mr. Umezaki (Hiroyuki Sanada), doesn’t make much sense once it’s revealed. If Umezaki has ulterior motives, why is it up to Holmes to reveal those ulterior motives? The resolution to the pre-WWI case is also weak—hinging, as it does, upon sentiment, and a heretofore unrevealed talent of Holmes to understand absolutely nothing about human nature.

The whole movie, in fact, turns on this notion. It suggests that while Holmes was good at “doing the thing,” he didn’t know people. It further suggests that at the age of 93, he finally kinda gets it. And he uses what he’d forgotten about his last case to make things right in the present day—both in England and in Japan. Essentially he realizes that a soft lie is better than the hard truth.

The plot thins.

The movie is directed by Bill Condon, who directed McKellen in “Gods and Monsters” nearly 20 years ago, and who has since directed other reasonably good movies: “Kinsey,” “Dreamgirls,” “The Fifth Estate.” This one, too, is reasonably good. But just that.

But we’ll always have Portsmouth.