[Kristen Bell talks about growing up with Veronica Mars.]

Opening during Veronica’s junior year at Neptune High, the series originally stood out for its clever and literate writing and the superior performances of Bell, Colantoni and Dohring. (Rob Thomas, the show’s creator, still oversees it and wrote the new season’s first and last episodes.) It was perhaps even more unusual for the way it presented a teenage world, and a story hinging on teenage melodrama, from a wised-up, adult point of view and with a fully adult emotional sensibility.

The adult intelligence is still there, and Bell and Colantoni are still wonderful together, consistently nailing the old-Hollywood, tough-and-tender style the show demands and demonstrating seemingly effortless comic grace. But Thomas hasn’t found a really satisfactory replacement for the show’s loss of teen spirit; and the grown-up romantic travails of Veronica and Logan, a significant subplot in the new season, aren’t as compelling as their tempestuous high school amours.

It’s also a problem that the streaming-season model entails stretching a single mystery over close to eight hours. That’s new for “Veronica Mars” — the network seasons had long-arc mysteries, but they were broken up by lighter stand-alone cases over their 22 episodes. Thomas has put together a complicated caper in Season 4, with the bombings simultaneously investigated by Veronica and Keith, the hapless Neptune police, a group of true-crime nerds, a pair of Mexican cartel hit men and Matty, a young woman who evolves into Veronica’s protégée. (Played by Izabela Vidovic, Matty fills the vacuum left by Tina Majorino’s pugnacious Mac, the one central character who doesn’t return.) Some of the twists are clever, but in the eight-episode format the story’s implausibilities are more distracting. The seams show in a way that didn’t used to matter.

(There’s another more directly annoying consequence of the move to streaming: several obtrusive product placements for Hulu itself, including a scene in which Veronica and Logan settle in to binge the last show you can imagine them watching, the British costume drama “Harlots.”)

Still, whenever the love story starts to drag or the mystery gets irritatingly convoluted, and despite an abrupt (and seemingly convenient) late detour into tragedy, “Veronica Mars” finds ways to charm you. Bell’s sparkle — no one does pluckiness better, or funnier — and Colantoni’s utterly relaxed, jazzlike timing are givens. Old favorites like Daran Norris, Duane Daniels and especially Max Greenfield make their usual solid comic contributions. (The chemistry between Bell and Greenfield puts a spotlight on the show’s failure to grow Dohring’s character into an interesting adult.) The show has fun with its own history, as in a touching scene when Daggs’s Wallace, now a teacher, watches Matty extract information from a love-struck mark just like Veronica used to when he was her high-school accomplice.