Sheldon’s obsessions led to a major personal discovery — and a big step forward — on The Big Bang Theory 9×10.

You soften my life with your love

In “The Earworm Reverberation,” Sheldon becomes convinced he is losing his mind when an unidentifiable musical refrain gets stuck in his head. He spends most of the episode trying to simultaneously identify the tune, and prepare his future, soon-to-be-demented self for this mad, mad world.

But as it turns out, the earworm has a much deeper significance than a mere flirtation with insanity. Sheldon’s brilliant brain eventually does its job and identifies the tune as “Darlin'” by The Beach Boys — but he doesn’t stop there. The true source of the earworm turns out to be more emotional (actually, much more emotional) than we ever would have expected from Sheldon.

In spite of The Big Bang Theory’s extremely rocky presentation of Sheldon and Amy’s romance (Sheldon has frequently ignored, mistreated, and disrespected Amy, which culminated in his tantrum-like refusal to accept their breakup), Sheldon comes to realize that “Darlin'” is, for him, a song about Amy.

He loves her. He misses her. And his life is poorer without her.

(We could have told you that, Cooper.)

Flush with his new understanding, Sheldon interrupts Amy’s date with British Dave — on the very night Amy had been considering losing her virginity. But when Dr. Cooper transforms from a borderline-senile scientist whom Penny and Leonard must treat like a child to a surprisingly amorous caller, Dave doesn’t stand a chance.

Amy and Sheldon confess their love, and kiss, and kiss, and kiss.

If Sheldon had been a fraction this mature for the rest of the season, we might even be cheering.

Crazy for you

Meanwhile, Raj and Howard have their own music-related challenges to deal with in “The Earworm Reverberation.” Raj takes the liberty of setting up a fan page for their band, to which Howard objects until he finds that “Footprints on the Moon” has one, apparently very cool, enthusiast.

Having been deprived, due to circumstance and social aptitude, to this kind of affirmation for most of their lives, Howard and Raj promptly go a little nuts. They stalk their fan all over social media, until they are really more of a fan of their fan than the other way around.

Alas, this time the rule about meeting people from the internet applies. Howard and Raj stalk Mr. Fan to a coffee shop and wait nervously for him to recognize them.

But then the guy turns out to be a public nose-picker. Appalled at what they have attracted, the duo behind “Footprints on the Moon” flee the coffee shop, leaving their confused fan behind.

How did you react to the events of ‘The Big Bang Theory’ 9×10?