Warning: Minor spoilers for "The Leftovers" ahead.

Imagine 2% of the world disappeared one day.

But they didn't die. They didn't contract a deadly virus, nor were they killed in a terrorist attack or the victims of a devastating natural disaster.

Instead, roughly 140 million people around the world vanished into thin air. Babies disappeared from strollers, the drivers of cars evaporated (leaving their vehicles behind and causing accidents), and even the Pope vanished from the Vatican. The event is clearly supernatural, defying the laws of physics as we know them, but no clear reason for how or why those people disappeared is provided.

There is no explanation — and there never will be. No one will ever know what happened to the roughly 140 million people who are no longer on Earth.

That is the opening premise of "The Leftovers."

The starting point for the series

"The Leftovers" is based on a novel by the same name, written by Tom Perrotta in 2011. HBO acquired the rights to the show soon after the novel was published, and brought on Damon Lindelof (co-creator of "Lost") to help adapt the book for television.

From the start, Perrotta assured his readers that the book would never answer the biggest mystery of all: What happened to all those people?

Instead "The Leftovers" (both the book and the TV show) examines how people would cope with, as Perrotta puts it, the "apocalyptic anxiety" of uncertainty. The mass disappearance is referred to as the Departure, while those who vanished are called the Departed.

The main players

The main characters in the series all revolve around the Garvey family. Though no one in the Garvey family were among the Departed, their lives (and the lives of everyone) changed drastically after the Departure.

Justin Theroux delivers incredible performances as Kevin Garvey. Van Redin/HBO

Kevin Garvey (played by Justin Theroux) is the police chief in Mapleton, New York. His wife, Laurie, abandoned her family to join a cult called the Guilty Remnant, or the GR.

The GR's "mission" is to force people around the world to remember the Departure, instead of potentially moving on or repairing their lives. They wear all white, live in communal houses, and don't speak a word. The only form of communication allowed is writing. The GR members also smoke cigarettes constantly, and stand outside the houses of people they decide to "target."

Liv Tyler plays Meg Abbott, one of the Guilty Remnant members. Felicia Graham/HBO

Another main character is Nora, whose husband and two children Departed, leaving her behind and alone. The odds of having more than one member of your immediate family (let alone three) were very low, so Nora has become somewhat famous in the post-Departure world.

Nora works for a new government organization called the Department of Sudden Departures (DOSD). This is another fascinating aspect of "The Leftovers" — the way the show explains how our entire society and governments would need to shift in response to the Departure.

Part of Nora's job is issuing questionnaires to people who claim they "lost" someone in the Departure. The uncertainty of what happened meant that life insurance companies didn't pay out policies, since the Departed didn't technically die. So the DOSD needed to conduct it's own investigations and issue separate payouts for families who lost someone.

The DOSD questionnaire is also possibly meant to serve as a research tool. After all, both the scientific and religious communities were eager to figure out exactly what happened to the Departed.

Which brings us to another central character — Matt Jamison.

Christopher Eccleston co-stars as Matt Jamison, a complicated religious man struggling in the wake of the Departure. Van Redin/HBO

Matt is a priest who believes the Departure was a test from God. In the years since the Departure, Matt has conducted his own mini-investigations into the Departed, trying to see what kind of people they were. He began uncovering various wrongdoings by the Departed, like men who gambled or cheated on their wives and women who were drug-addicts or convicted criminals.

He circulates fliers of these "bad" people in an effort to prove that the Departure was not meant to be the Rapture or an act of God meant to single out worthy believers. Instead, he thinks the Departure was a test from God to see how the people left behind would react. Would they abandon their belief in a higher power?

The GR is a formidable organization akin to terrorist groups. HBO

The risky writing makes the show incredible

Aside from the fantastic base premise Tom Perrotta wrote, the best part of "The Leftovers" is the big risks showrunner Damon Lindelof takes when it comes to storytelling. Without giving away any main plot points, we'll go through some of those risks here.

Each season features at least one "bottle" episode — a full hour that focuses solely on a single character. While this can be a bit disorienting sometimes, these always prove to be some of the most impressive installments in each season.

One of these episodes, "International Assassin," has been hailed by critics as an incredible feat of television magic. The episode draws on Dante's "Inferno" for inspiration, following a character as they battle their inner demons in a purgatory-like environment.

While some believe it held echoes of "Lost" — Damon Lindelof's other series that dealt with the afterlife — many more saw the episode as a transcendent TV moment. The New York Times called it "a brain-shredding masterpiece," while fans of the series can't stop raving about it on forums like Reddit.

An emotional scene from the magnificent "International Assassin" episode. Van Redin/HBO

The show's creators don't shy away from polarizing production choices, like completely changing the opening credit visuals and song for season two (so far we don't know if it will be different, yet again, for season three). In season one, the opening was ominous and abrasive with heavy religious overtones. The score was done by Max Richter, whose knack for drawing emotion from music is uncanny.

But — without warning — season two featured an uptempo song by Iris Dement with lyrics that spoke directly to the series' theme:

Everybody's wonderin' what and where they they all came from

Everybody's worryin' 'bout where they're gonna go

When the whole thing's done

But no one knows for certain

And so it's all the same to me

I think I'll just let the mystery be

And then there's the overall tenor of "The Leftovers." The show deals with a lot of heavy emotional trauma, and sometimes features brutal violence. Though this means sometimes it's not a pleasant or easy viewing experience, "The Leftovers" is an important study in human capacity for love, grief, and openness.

It forces viewers to consider their own beliefs about what comes after death, and how that should or shouldn't effect how we live. These big questions are focused down into intimate stories about individuals, which makes them simultaneously more digestible and more impactful.

Lindelof and his team decided to end the series after three seasons — which means newcomers to "The Leftovers" only need to catch up on two seasons (each made of 10 hour-long episodes) before the final season returns on April 16.

We're confident that this third and final season will be a remarkable final installment to one of the most unique shows currently airing, which means now is the time to jump on bandwagon. You won't regret it.