Music has always played an important role in Black Mirror, and Season 6 is no exception.

But why is "Beyond the Sea", an episode about long-distance space travel and earth-bound replicas set in the year 1969, named after a Bobby Darin song that doesn't really have anything much to do with space?

If we dig into the lyrics a bit, the whole thing starts to make a lot more sense.

SEE ALSO: 20 of the most WTF quotes from Season 6 of 'Black Mirror.' You'll cry — and laugh.

What is "Beyond the Sea" about?

One of the bleakest episodes of the series (and possibly the show as a whole), "Beyond the Sea" follows Cliff (Aaron Paul) and David (Josh Hartnett), two astronauts on a six-year space mission who have "Earth replicas" — basically robot clones of themselves — that they can sync their minds with in order to still (sort of) spend time with their families. Their real-life bodies stay on the ship, but they can transport their consciousness' back to their robotic Earth bodies via a machine, with the idea being that the mental toll from spending six years in space is lessened for the astronauts.

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As this is Black Mirror, though, things don't turn out that way. After David's family are murdered by a cult and his replica is destroyed, he starts using Cliff's in order to get a break from the isolation of the ship — and things get much, much worse from there.

Meanwhile, in the background, there's the song. During two scenes we hear Charles Trenet's "La Mer" (the original version of Bobby Darin's translated "Beyond the Sea"), first when David dances with his wife, Jessica (Auden Thornton), at the start of the episode, and then later when he — while inhabiting Cliff's replica –—dances with Cliff's wife, Lana (Kate Mara). So the song features in two key scenes that bookend the episode, but does that really merit it featuring as the episode's title? Well, there's more...

Can technology ever truly replace human connection? Credit: Netflix

What are the lyrics to the song "Beyond the Sea"?

The key may lie in the song's lyrics. Here are the first four verses:

"Somewhere beyond the sea
Somewhere waiting for me
My lover stands on golden sands
And watches the ships that go sailing

Somewhere beyond the sea
She's there watching for me
If I could fly like birds on high
Then straight to her arms
I'd go sailing

It's far beyond the stars
It's near beyond the moon
I know beyond a doubt
My heart will lead me there soon

We'll meet beyond the shore
We'll kiss just as before
Happy we'll be beyond the sea
And never again I'll go sailing"

There are a number of possible interpretations – Is the song about unrequited love? Is it about meeting a loved one in the afterlife? – but in the context of the episode, the meaning seems clear enough: "Beyond the Sea" is about the pain of being separated from a loved one by a great distance. These lines, in particular, stand out:

"If I could fly like birds on high
Then straight to her arms
I'd go sailing"

In the song, the writer is dreaming about being able to traverse an ocean like a bird in order to see his loved one. In "Beyond the Sea", that's essentially what the fictional technology at the heart of the story allows the astronauts to do. Even though there are presumably light years separating them from their families, they're able to traverse the distance in an instant using their replicas. The question the episode seems to be posing, though, is would this be enough? Can technology ever truly provide enough of a substitute for a physical connection?

In "Beyond the Sea", at least, the answer is clearly no — and it's particularly telling that the two times "La Mer" plays both occur just before things go horribly wrong.

How to watch: Season 6 of Black Mirror is now streaming on Netflix.