"He fought his first battle on the Scottish Highlands in 1536. He will fight his greatest battle on the streets of New York City in 1986. His name is Connor MacLeod. He is immortal." There could be only one Highlander, but there could be more than one Highlander movie. The original Highlander movie was released in 1986, and Highlander 2 in 1991. Both movies are basically sci-fi fantasy films. There were several more sequels produced and even a TV show that ran from 1992 to 1998. Focusing on the original release, reviews were mostly positive. The movie did not do well at theaters in the USA, but it fared well in Europe, which created enough buzz to make it a cult classic in the USA.
In the movie, immortal Connor MacLeod, played by Christopher Lambert, goes about the business of understanding his roots, with the help of fellow immortal Juan Sanchez Villa-Robos Ramirez, played by Sean Connery. There are a number of flashbacks between modern day New York City and other places/times in history, such as 16th century Scotland. It is in the 16th century where MacLeod receives his assistant from Juan.
Immortals must fight each other to the death, because as far as immortals go, only one can claim the ultimate prize (ultimate power and knowledge). This must take place at "the gathering", which is essentially the ultimate battle of immortals. In the end, "there can be only one". Death must be by beheading, and when the rival is killed, their power is then absorbed by the surviving immortal. Immortals recognize each other through a extrasensory perception called "the quickening".
By the end of the movie, there are only two immortals left; Kurgen and MacLeod. Kurgen's intention is to claim the prize, and he kidnaps MacLeod's new girlfriend, a reporter named Brenda. Using her as bait, Kurgen draws MacLeod into a battle. MacLeod prevails, and the prize is his. Part of the prize is mortality, in addition to having a pantheistic connection to everything in the world, and thus he is able to settle down, have a family, and die like the rest of us. Which, ultimately, is all he wanted.