Finally, in a world of confusion, the last episode of Lost has finally brought a certainty. Or maybe should I say a constant? After three seasons and four episodes, we finally have a real clue: there is something terribly wrong with the time on the Island and its surroundings.

In The Constant, the story picks up from where we’re left in the third episode. Desmond, Sayid and the pilot are heading to the freighter on board of the helicopter.

However, as they pass through an electromagnetic storm, Desmond’s mind got disconnected. As his body stays in the helicopter his mind travels back in time in 1996 when Desmond was in the army.

When his mind finally heads back in the present days, Desmond has no recollection of the Island and he doesn't know why is he in the helicopter.

The three guys will land on the famous freighter (which, if you ask me, looks kind of creepy), while Demsond’s mind seems to be on vacation, traveling back and forth.

Meanwhile in a short sequence, back on the Island, Michael Faraday reveals himself as the man who holds all the answers, or at least some of them.

"Your perception of how long your friends have been gone, it's not necessarily how long they've actually been gone," Faraday says to Jack, a phrase that can be the motto of the episode.

Back on the freighter, as the two not-so-friendly guys, Keamy and Omar, put Desmond in the freighter’s sick bay, the story starts to become clearer.

The 1996’s Desmond calls his beloved Penny, telling her how he is confused. Penny refuses to talk to him and Desmond is back on the freighter, locked in the sick bay together with George Minkowski, the former transmission officer of the ship, who is experiencing the same phenomenon as Desmond.

Meanwhile, Sayid notices that there is something definitely wrong with the time: the helicopter left the Island at dusk but arrived at the freighter in plain midday even though the freighter is only 40 miles away. He trades his gun with the pilot to obtain a phone to call Jack. When Faraday hears about Desmond’s delusions, he asks to speak with him. Sayid heads to the sick bay and now the real clue kicks in: Faraday has met Desmond back in 1996.

Faraday, who seems to know exactly about Desmond’s mind traveling is going through, tells him to meet with 1996’s Faraday.

Back in 1996 and in another flashback, Desmond meets Faraday at Oxford. And their meeting is the key to the whole episode: the time travel.

The episode, which seems to draw much of its inspiration from H.G. Wells’ short story "The Remarkable Case of Davidson's Eyes" (e-book) poses an interesting question: what if a time travel means only that your mind will become aware about the future? Your physical body continues to exist in different times, but is truly the mind, which connects them.

How could this type of travel be obtained? Of course, by exposing someone to a strong electromagnetic field with certain properties.

But there is a downside to the whole thing. The side effect of the time/mind traveling is the irreversible effect on the brain, which will eventually "crash," if…you are unable to have a constant.

As who or what could be a better constant for Desmond than his one true love, Penny?

Back on the ship, Keamy takes the phone back from Desmond and locks Sayid in the sick bay. He and Omar then bring Frank outside the room, as the captain wants to talk to him. Sayid adds that he too wants to talk to the captain, to which Keamy answers sarcastically: "I'll be sure to let him know. In the meantime have a seat."

When Minkowski, who is lying in bed in plain confusion, hears Sayid calling Desmond by his name, he suddenly awakes in the present. He tells Desmond that Penny has constantly called the ship, but he wasn’t allowed to answer and now the equipment is broken.

Back in 1996, Desmond is trying to find his constant. He gets is touch with Penny’s father, Charles Widmore, at an auction and he manages to convince him to give away Penny’s address. Charles Widmore has joust bought the ledger of Black Rock’s first mate (yes the same Black Rock that is on the Island) and he is in good mood.

On the ship, Desmond, Sayid and Minkowski are heading to the transmission room to call Penny. Suddenly Desmond realizes that he is in 2004 and he needs to find Penny’s phone number.

Meanwhile, Minkowski, who does not have a constant to keep him safe, dies of a brain aneurysm.

In 1996, after his conversation with Charles, Desmond visits Penny, begs for her number and implores her not to change it in the future eight years, because he will call her…in about eight years on Christmas’ Eve.

Sayid fixes a phone and now we are all ready for the grand finale: Desmond calls Penny and she answers in the best scene I witnessed so far on Lost since the plane crashed on the Island.

After eight long years and after he has been through the helland back, Desmond finally hears Penny’s voice and their conversation (together with this episode of Lost) deserves an Emmy for one of the best love scenes in the history of TV series.

There are four minutes of pure magic on the screen, in a scene that reminded me of Humphrey Bogart and Ingrid Bergman in the last scene of "Casablanca" (ok, ok maybe I’m exaggerating a little, but believe me it’s totally worth watching the whole damn Lost for this scene).

Unlike the other four episodes, The Constant ends without any mind-blowing twist. However, we will find out that Desmond is Faraday’s constant.

As for Lost, now that the time travel has officially been introduced into the plot, we can expect anything.