The second installment in Rian Johnson's Knives Out franchise features Daniel Craig as Detective Benoit Blanc once

more and a twisty whodunnit murder mystery. But the movie isn't called Knives Out 2—it's titled Glass Onion: A Knives Out Mystery.

So why is the sequel called Glass Onion? First, director Johnson was inspired by a 1968 Beatles song,

and plays the song over the end credits of the film. "It's kind of a Beatles song about a mystery that's not actually a mystery," Johnson explained to Reuters.

The song features intentionally confusing lyrics that mean nothing, like "Well here's another clue for you all / The walrus was Paul."

They also sing "Looking through the bent-backed tulips /To see how the other half live / Looking through the glass onion." 

As John Lennon explained later, "I was having a laugh because there’d been so much gobbledygook about [Sgt. Pepper album]—play it backwards and you stand on your head and all that."

Johnson wanted the title to include "glass," because the mystery is something hidden in plain sight.