Gil Grissom (William Petersen) returned to “CSI” to talk to bees, lecture about whale songs and tell of a flower whose fragrance can make anyone lose control. For a final time, Grissom’s offbeat brilliance brightened the forensics work.

As the influential CBS crime procedural ended its 15-year run - SPOILER ALERT - Grissom also stopped a mad bomber and found personal happiness. Petersen’s return was a reminder that “CSI” had never been the same since Grissom left.

An oft-repeated promotional spot signaled the ending. After working a final case, Grissom realized he wanted to be with ex-wife and former colleague Sara Sidle (Jorja Fox). She joined him in the final moments, and they sailed away.

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But when Grissom faced off against the villain, the bad guy was no match. Grissom paused to talk whale songs, and Petersen sold the unusual moment. The actor had been a chief reason the show took off in the ratings.

The flashy technology and detail-driven crime stories were others. In the end, the finale highlighted the series’ assets that made the “CSI effect” part of the culture. The scenes ranged from horrifying (those bombings) to gross (a look at the contents of a cadaver’s mouth) to melodramatic (Sara lost it in talking with Lady Heather).

There was business to conduct: D.B. Russell (Ted Danson) announced he was moving on for another opportunity. He joins “CSI: Cyber.”

The “CSI” finale played tricks, too: Grissom came up on a corpse that turned out to be … synthetic. “Everyone thinks you’re responsible,” Grissom told Lady Heather of the bombings. “I am,” she replied.

But, of course, she wasn’t. Grissom, however, did thank her for opening his heart and making him realize his love for Sara.

Now they live in TV history, sailing away and enjoying a happily-ever-after that will not end. After all that forensics, why not love?