From the beginning, Mr. Spock was the conscience of “Star Trek,” and Leonard Nimoy was the actor who transcended all of the sci-fi trappings to deliver on the challenge of portraying a character who claimed to have no emotions.

Nimoy brought to Spock the depth and complexity that made viewers immediately intrigued with the stern-faced Vulcan, the first officer and right hand to William Shatner’s larger-than-life Captain Kirk. “Star Trek” devotees cheered when Spock’s beloved logic would save the day, and they wept when he died (sort of) in “Star Trek II: The Wrath of Khan.”

But it all began with Nimoy’s work in 79 episodes of the original series that aired on NBC from 1966-69. Here are some of the highlights of Mr. Spock’s “Star Trek” career in the original series and beyond.

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Amok Time

The legend of Spock and the bond between Spock and Kirk doesn’t get any deeper than this season-two episode that offered copious backstory for Spock. It introduces the concept of mating ritual “pon farr” — aka the Vulcan version of the seven-year itch — and features a hell of a fight scene between Spock and Kirk. It also treats fans to a glimpse of Spock lowering his logic guard when he realizes that Kirk is not dead.

City on the Edge of Forever

Spock shows great empathy when Kirk falls in love (with Joan Collins) after they wind up traveling back in time to 1930s America. And of course Spock’s electrical wizardry saves the day and helps them escape the time warp.

The Menagerie Parts 1 and 2

Spock faces a court martial in his elaborate dedication to helping his former Enterprise leader, Capt. Pike (aka the star of the first “Trek” pilot). It’s a season one two-parter that helped establish the show’s reputation for intense drama and plot twists.

The Devil in the Dark

Spock flexes his paranormal muscles by mind-melding with the Horta. His Method acting training is put to good use as he channels the emotions of the oddly shaped animal.

This Side of Paradise

Spock lets his hair down and falls for guest star Jill Ireland after the Enterprise visits a planet where strange plant spores make him suddenly blissfully content.

Star Trek II: The Wrath of Khan

Nimoy had many memorable moments in the first six “Star Trek” movies – none more so than his death at the conclusion of the well-reviewed “Star Trek II: The Wrath of Khan,” highlighted by Ricardo Montalban’s understated performance as the vengeful Khan. But Nimoy’s focus in the death scene makes it a true tearjerker. Using his Vulcan logic, Spock sacrifices himself without hesitation for the crew and dies of radiation poisoning.

Two years later, in “Star Trek III: The Search for Spock,” the character is successfully resurrected at the end of the movie on the planet Vulcan. It was Nimoy’s feature directorial debut.