Last night's Warehouse 13 was short on the silly humor the show has made its wheelhouse lately — although there was a bit of fun with Pete was boxing — and instead long on the kind of sentimentality that would feel like ridiculous overkill on most TV shows. And yet, on Warehouse 13, it more or less works perfectly. (Although it dances right up to the edge.)

Why is Warehouse 13 able to pull off scenes like the one above, without feeling manipulative or self-indulgent? (Spoilers below.)

For the most part, it's because the writers and actors have done such a great job of fleshing out these characters, they can go to some pretty cheeseball places without feeling like we're being slapped with a rubber chicken of sentiment. Take last night's episode — the business about Steve Jinks' dead sister has been built up since the character was first introduced, so this wasn't entirely an out-of-nowhere revelation. The bond between Steve and Claudia has been pretty painstakingly developed as well. And the notion that Steve, a Buddhist, would turn out to be kind of a vindictive twerp with vengeance in his heart, feels like layers of character-development rather than a contradiction born of carelessness.

Plus, the whole "Steve goes home to mom" storyline benefits from some really strong acting — Laura Innes has been wasted in drek like The Event so much lately, you almost forget what she can do when she's handed some real material. The scenes where she's trying to reach out to the completely closed-off Steve, with a brittle patience, are really terrific. She gets a lot out of a line like, "I don't want you out of my hair," without milking it at all. And Aaron Ashmore and Allison Scagliotti are great, as always.

But also, the whole concept of Warehouse 13 is increasingly one that lends itself to a certain amount of sentiment — the artifacts are increasingly being shown to be created by emotion and linked to people's emotional states. In this episode, the key to freeing Steve from the metronome that resurrected him is basically for him to work things out with his mom and have a catharsis where he has a moment of pure love for her. Meanwhile, in the ostensible "A" plot, a steelworker/boxer has a shard of ancient sculpture in his heart that gives him superstrength and makes people turn to rust — which is triggered by strong feelings.

Oh, and there's also the fact that this show really does feel sincere, in all of its slightly goofy optimism about people. When sentimentality feels overblown or fake, it's usually because you can tell that people are putting it on. Classic Hollywood sentimentality is often a thin shell over a bottomless well of loathing for the characters, but this show invests a lot of inventiveness into showing how good people can win out by helping each other and being clever — similia to the way Eureka often did.

In this particular episode, self-sacrifice is the key to success in both the "A" and "B" plots — although Pete really doesn't need to let the boxer/steelworker/Marine beat him to a pulp, since Myka already has things under control.

All in all, this was another really strong episode, which went places where most TV shows would falter.

Oh, and in the "C" plot, Artie finally hashes things out with Mrs. Frederic and H.G. Wells (plus Leena), and they pretty quickly sort out some stuff that Artie has been stuck on for weeks. Like, Claudia stabbing Artie with the magic knife probably isn't the super-awful evil that Brother Data warned about. And Brother Data probably just told Artie not to tell anybody about the astrolabe as part of his overall campaign to isolate Artie. Oh, and I love the matter-of-factness with which Mrs. Frederic tells Artie, "I would have done the same." No hand-wringing — Artie did the right thing, let's move on.

And then there's a coda, where Mrs. Frederic gives H.G. Wells the astrolabe and tells her to disappear, because she's already figured out that something might not be quite right with Artie. (Although, at the end, when Mrs. Frederic turns and gives a weird look to the camera, is that a hint that this isn't really the real Mrs. Frederic?) In any case, the preview for next week's episode seems to show Artie turning into Brother Data, which is either the thimble at work or proof that you guys were right all along and Artie is stealing from himself. We'll find out soon!