Noah Hawley tells THR about the new voice along for the ride in the second year of FX's mind-bending Marvel series.

[This story contains spoilers from the season two premiere of FX's Legion.]

About a third of the way through its first new episode in more than a year, Legion shifts gears in a rather surreal way: a new chapter, called "Delusions," begins as a disembodied voice — and a very familiar one at that — explains the definition of the quoted word in question, by way of a fable.

"And now we must speak of Zhuang Zhou, who fell asleep one day and dreamed he was a butterfly," says the voice. "For hours, he fluttered in the warm winter sun until he no longer remembered he was Zhuang Zhou. Suddenly he woke, and he was Zhuang Zhou again. But in that moment, he didn't know: Was he Zhuang Zhou who had dreamed he was a butterfly, or a butterfly who was dreaming he's Zhuang Zhou?"

The voice guides the viewer through further examples of delusions, posing a chicken-and-egg dilemma that gives birth to an oil-slicked monster. Arresting as the visual splendor may be, it's the voice that leaves the biggest impression. "Who is that, and why does he sound so familiar?" If you're asking that question, here's some good news: you're not going slowly mad. The actor is indeed someone with a "Mad" reputation.

Final spoiler warning, as we reveal the man behind the curtain …

…or the "Mad Man" behind the curtain, if you'll forgive us a bite of low-hanging fruit.

That's right: Jon Hamm is aboard the good ship Legion this year to narrate what creator Noah Hawley describes as "educational segments," studded throughout the season. The scenes are designed to highlight the fundamental theme of season two: turning David Haller's (Dan Stevens) battle against the "enemy within" into an examination of the "enemy without," in Hawley's words.

"The Shadow King (played alternately by Navid Negahban, Aubrey Plaza and Jemaine Clement) has left him and is on the hunt for his own body," the Fargo and Legion mastermind tells The Hollywood Reporter about his greater vision for season two. "But I didn't necessarily want it to become a good versus evil or white hat versus black hat situation, a typical collision course: 'Let's fight!' If the first season was about looking at individual mental illness — whether David had schizophrenia or he had these abilities — then the second year is about the greater idea of mental illness. What if the world has gone crazy, and he's the sane one? I was interested in the idea of our shared reality being a choice that we make. Sometimes societies go a little bit crazy. How does that happen? Part of exploring that involves inventing these educational segments about trying to explain and visualize what is a delusion: By saying delusions are ideas, and ideas are like an egg, and some ideas are healthy while others are unhealthy. Witness the baby chick that comes out of the first egg, and the horrible thing that comes out of the second egg. It was really about trying to take these concepts of mental illness, and visualizing them in a way where you can tell a story."

Which brings us to Hamm's role as the narrator of the educational segments. How did the erstwhile Don Draper wind up giving voice to Hawley's surreal superhero series? According to the creator, it was as simple as a quick phone call.

"I got to know Jon a little bit in the last year," says Hawley, who has been preparing to collaborate with Hamm on the feature film Pale Blue Dot, co-starring Natalie Portman. "I had written this narration for the first hour, and it started to feel like it would be in every episode. You always want a great voice for that, and I didn't think it should be one of our characters. You think about Alec Baldwin in Royal Tenenbaums, and you think to yourself: 'I need that voice — the great voice.'"

Which led Hawley to an obvious conclusion: "Of course, Jon has a great voice. So, I asked him, and he said yes." Which itself led to another development. "[Hamm's] agents then went, 'Why didn't you ask me first?'" Hawley recalls with a laugh. "I don't know! If I have his phone number, I'm going to call him!"

In bringing Hamm into the Legion fold in this disembodied capacity, Hawley sees season two's educational segments instantly possessing "a sense of identity and a feeling of control. You really feel like the show itself has a point of view and it's all going somewhere, as opposed to either a random narrator or having one of the characters themselves narrate it. The narration feels a little tainted when it's coming from [a character's] point of view."

With that said, don't expect to see Hamm onscreen this season beyond the narration. "I'm pretty confident that he's just a voice this year," Hawley says — an answer that, in this writer's interpretation, leaves some wiggle room for a flesh-and-blood appearance from the Mad Men actor further down the Legion line.

What did you make of Hamm's appearance in the Legion premiere, and what are your theories for his involvement moving forward? Sound off in the comments section below, and keep checking THR.com/Legion for more.