“Masters of Sex” turned out to be a wonderfully clever act of deception – a period soap opera, set against an organically salacious backdrop. This Showtime drama about the pioneering work of sex researchers Masters & Johnson returns for a second season with all of its charms intact, juggling an assortment of plots built around sexuality, including the inherent lie in how the principals try to characterize their ongoing affair as “research.” In that respect, at least – the idea that sex can’t be clinically divorced from emotion – this handsomely produced series is about as conservative as anything on TV.

Just to recap season one, ob-gyn/sex researcher Bill Masters (Michael Sheen) was finally ousted from his hospital when he presented his sex study, leaving research partner Virginia Johnson (Lizzy Caplan) in the lurch, while wearing a scarlet “S” for role in the project. This, despite Masters’ knowledge of the fact his longtime mentor and friend Barton (Beau Bridges) is a closeted homosexual, something he’s been desperately trying to hide from his wife (Allison Janney, like Bridges, moonlighting from a full-time sitcom gig on sister network CBS).

As the second season begins, Masters moves on to a new position and a new employer (Danny Huston), allowing him to maintain his work, with conditions. Virginia and Bill also continue their trysts, unwilling to acknowledge what’s happening between them; and Barton seeks to “cure” his impulses, which would seem more like a relic of the 1950s if the notion of “reparative therapy” wasn’t still popular in places like Texas.

Michael Apted directed the first three episodes of the new season, and while the first two dutifully move the plot and story along, the third is the real standout: Taking place almost entirely in a hotel room, the hour finds the reticent Masters opening up about his painful upbringing and Johnson reciprocating in kind, underscoring just how terrific these two actors are and the budding depth of their relationship. Indeed, given how guarded both characters are emotionally, it’s particularly striking to see them baring themselves figuratively as well as literally.

Showrunner Michelle Ashford has brought some new elements into season two, including a subtle exploration of race and class through the arrival of a young African-American nanny (Keke Palmer) hired by Masters’ wife (Caitlin Fitzgerald), who remains one of the more tragic figures in the story. Sarah Silverman also joins the show later in the season.

Ultimately, though, “Masters of Sex” remains driven by its central duo, and the protracted tension not just associated with the Eisenhower-era response to their work but the inevitability of where their personal story is heading.

The come-on of the title notwithstanding very little about that is groundbreaking, or even surprising. But it is, almost without exception, highly watchable and entertaining.