In the Highlander franchise, human beings born with the power of "the Quickening" become immortal if they suffer a premature death by unnatural means (such as by violence).
One day, the last few will fight during "the Gathering" and the survivor will win the Prize, the collected energy of all immortals who ever lived, enough power to conquer or destroy humanity.
Highlander: The Series introduced the idea that the lives and actions of immortals are recorded by a secret order of mortal humans known as the Watchers.
According to Widen, "The idea of the story was basically a combination of a riff on The Duelists – [a Ridley Scott film where] guy wants to finish a duel over years – and a visit I made both to Scotland and the Tower of London armour display, where I thought, 'What if you owned all this?
"[1] According to William Panzer, producer of Highlander: The Series, "And that's where everything fell into place — the idea that there are immortals and they were in conflict with each other, leading secret lives that the rest of us are unaware of.
"[3] This seems to be a metaphor, as there are several immortals in the series raised by their natural parents and there is no indication in the movies that Connor MacLeod was adopted.
Taking place in a future world where society across Earth has fallen to violence and chaos, Duncan MacLeod and others investigate the Source of immortality, an energy well hidden in Eastern Europe.
"[4] Highlander: The Series producer William Panzer said, "for the most part, immortals are very much like ordinary people...[5] Some make a lot of money.
In the original film Highlander, the villain known as the Kurgan attempts to behead Connor MacLeod and take his Quickening before the young Scotsman can discover his immortality and become a trained warrior.
In the original movie, old friends Kastagir and Connor know that they are two of the last three immortals left on Earth, the third being the evil and powerful Kurgan.
When the immortal Ramírez is showing Connor MacLeod their abilities to survive deadly forces and to sense the emotions of living things around them, he refers to these powers collectively as "the Quickening."
In the original movie, Connor MacLeod (after being alive for over 400 years) shows keen insight into the feelings of people around him, and when entering the home of a person who doesn't trust him, he instantly knows where she would have hidden things in the room, such as a weapon.
They hope that if they do this long enough, they will eventually be the last one alive, earning the Prize, the total collective Quickening energy of every other immortal.
This same film, and certain episodes of the TV series, indicate that rare immortals may also have other seemingly supernatural powers, such as sorcery or clairvoyance.
Characters often use the term "Quickening" to refer to the actual process of an immortal's energy being released after losing their head.
Series actor Adrian Paul explained, "The Quickening is the receiving of all the power and knowledge another immortal has obtained throughout his or her life.
"[9] In Highlander: The Series, it is said that the immortal who survives a duel with another will not only absorb power but also some physical skills and can temporarily experience personality traits and flashes of memory from the one beheaded.
In the same episode, Duncan MacLeod reveals that some immortals speak of this phenomenon as a "Dark Quickening", when the personality is overloaded and corrupted.
The TV production crew and promotional materials included with the DVDs of Highlander: The Series refer to people who have the potential to become immortal but have not experienced their First Death yet as "pre-immortals".
"[10] The movie Endgame establishes that the process is trigged by the "shock of a violent death" and that without such a trigger the pre-immortal person will simply age and die as other humans.
In the live-action TV series, immortals have no access to their powers at all until after the First Death, including the Buzz which allows them to sense others of their kind.
[13] In the first film, Connor and the Kurgan are invincible to all injuries and heal quickly, allowing them to shrug off fatal gunshots without much pause (though they do feel pain).
In Highlander: The Series, immortals cannot die permanently unless beheaded but they can still enter a temporary death-like state if they suffer fatal actions such as drowning or loss of blood or hanging.
"[20] In the original film Highlander, the warrior Ramírez says that immortals will fight and kill each other and take each other's power until "the time of the Gathering."
In Highlander: The Series, protagonist Duncan MacLeod believes during season 1 that the time of the Gathering is drawing near, as there are not many immortals left alive (relative to the number that used to exist).
When the film showed Connor MacLeod winning the Prize in 1985, he became a mortal man, now able to age and father children, and his connection to nature increased to the point that he could now know the thoughts and dreams of any living person on Earth.
"[12] Earlier in the film, his mentor Ramírez warns that if an evil person were to gain the Prize, they would become powerful enough to enslave humanity to an "eternity of darkness" (Ramírez understood the power that the victor would gain but seemed unaware that they might become mortal in the process and die of old age if not sooner, so his belief that their rule over humanity would be eternal is understandable).
"[22] In the alternate timeline of Highlander: The Animated Series (1994-1996), immortals find a way to transfer Quickening energy to each other without dying in the process.
In the film Highlander III: The Sorcerer, two immortals are dueling near a Buddhist shrine when one of their swords explodes and as wind suddenly rises around them.
In the TV series episode "Little Tin God", the character Joe Dawson describes a legend that says that the eruption of Mount Vesuvius was caused by "two Immortals going at it in a Temple of Apollo" in Pompeii, breaking the rule.