Before the 1996 SUPERGIRL series, Linda Danvers was a human girl in her late teens living with two perfectly ordinary parents in the not so ordinary small town of Leesburg. A talented artist, Linda viewed Supergirl as her role model and frequently found herself sculpting the superheroine's form. But an evil demon named Buzz had played upon Linda's loss of faith in those around her by drawing her into his cult, in preparation for using her as a human sacrifce to an otherworldly creature known as Lord Chakat. Unbeknownst to Linda, Buzz's plans for her went much deeper than that, and the ritual sacrifice was intended to draw in Supergirl. Supergirl managed to reach Linda before the sacrifice was completed, but not in time to save her life. With Supergirl filled with grief over her failure, and Linda feeling overwhelmed at how her life was ending before she could set right what had gone wrong, the two reached out to each other at the moment of death and Supergirl merged her protoplasmic form with that of Linda's. The two beings became one.
Kara, the original Supergirl from Krypton, had died during the Crisis on Infinite Earths (1985). The memory of her existence was erased when the multiple worlds combined into one at the end of that first Crisis (it happened again in 2005's Infinite Crisis, but that time Supergirl survived). The Supergirl identity was reintroduced in the comics a few years later, this time as a genetically created being who had been given the name "Supergirl" but was unrelated to Krypton (see Matrix and Matrix Comics). She had no connection to Kara or Superman, but made her place on Earth as best she could. Still she felt she lacked something, a "soul" in a way. Her impulse to merge with Linda gave her that soul, and much more. As Supergirl/Linda struggled to reconcile her two lives, two sets of memories, and two very different characters, she also found herself manifesting new powers: she had become an Earth Born Angel. Eventually it would be Linda's personality that came to dominate, but not before Supergirl learned that Karahad been Linda's "guardian angel" since childhood (SUPERGIRL #49). Kara had been with her all along, waiting for her destiny to find her. More than just a replacement for Kara, Supergirl had been reborn.
The Matrix Supergirl had never really found a place in the DC Universe; it was clear that no one at DC Comics had a good idea of who she was or could be. This all changed when Peter David was given a new Supergirl series and brought to it a very clear vision and plan for Supergirl. Fortunately he was able to remain on the series for its the entire run. His series launched in 1996 with a shocking first issue: in it, Supergirl merges with a dying human girl named Linda Danvers, taking on her identity and very human complexities.
The origins of the second Supergirl are very different from the original Kara/Supergirl, but the Peter David series cleaned them up and made Supergirl into a sympathetic, strong, and fascinating hero. The series did something no other Supergirl series or comic had ever really done: treat Supergirl as a serious, intelligent character. The writing set a high bar against which to judge all past and future treatments. I found this Supergirl far stronger and more engaging than the Supergirl of the 60's-80's, and especially the Matrix Supergirl of the late 80's/early 90's. Following the storyline was quite a ride. Right from the surprisingly excellent debut issue, this series explored Supergirl's character as a multi-faceted and very grounded superhero, presenting her with intriguing adventures, challenges, and personal growth (all frequently of a mystical nature) to an extent never before seen in the Supergirl comics. Yet it also built on Supergirl's history, a rarity in DC Comics.
The series focused on long-running story arcs that developed its heroine and took her in bold new directions that constantly challenged the reader.
Supergirl is Linda Danvers, but this isn't just a secret identity which she has taken as a cover for her superheroics. Prior to meeting in issue #1, Linda was an ordinary teenager living in the small town of Leesburg, while the superhero known as Supergirl was a shapeshifting artificial being with the memories of another world's Lana Lang, endowed with superpowers both similar to and very different from Superman's (see History for more about the death of the original Supergirl and the origins of this new Supergirl). She became known as Matrix and had telekinesis, invisibility, and shapeshifting as her main powers. Both Linda and the alternate universe Supergirl found what they had been searching for, within the other: Supergirl felt she lacked a soul and a human identity and Linda lacked a sense of hope and purpose.
Through
a convergence of supernatural events, Linda Danvers and Supergirl were brought
together in a merging of physical form and consciousness that brought a new
meaning to both their lives. A new, two-in-one, Supergirl was born. Supergirl
now has a past as Linda Danvers and a human family, with all that entails,
and Linda Danvers is now endowed with superpowers of flight, superstrength,
and the ability to transform into Supergirl whenever the world needs saving.
This event has had far-reaching repercussions: Supergirl is now more powerful
than ever, for the act of giving her life for another caused her to become
an earth-born angel. The Girl of Steel found herself with wings of
flame and an even greater role as the Angel of Fire.
In issue #50 Supergirl fought with her two fellow earth angels, also joined beings, in the climactic battle to defeat the first vampire, the Carnivore. In defeating this powerful demonic being who had been her nemesis for fifty issues, Supergirl lost her Earth Angel aspect and attending angelic powers. Amazed that she had survived, but realizing that her "Supergirl" half had been separated from Linda Danvers, she found herself with reduced superpowers and thus began a quest to find the "missing" spirit of Supergirl/the Earth Angel. This ended her "Angel of Fire" phase. The Earth Angel-Supergirl was captured and imprisoned in the Garden of Eden by Lilith, the "mother of demons". This left Linda-Supergirl with the problem of convincing everyone who had seen Supergirl "die" that she was, indeed, Supergirl. She acquired a new costume which she keeps to this day, but she now looks physically like Linda Danvers (shorter, smaller features, blond wig, etc).
Linda continued to kick butt as Supergirl from issues #51-74, travelling with Buzz (former demon turned sidekick) and Mary Marvel and following the Chaos stream in search of the missing Supergirl/Earth Angel. Finally in issue #74, Linda confronted Lilith in a big showdown, including a heated battle between Linda-Supergirl and Earth Angel-Supergirl (who was being controlled by Lilith). The Angelic Supergirl broke from Lilith's hold and destroyed Carnivore once and for all, Buzz killed Lilith, and Linda died briefly. Matrix/Supergirl in her earth angel form offered to merge with Linda once again to save her, but Linda heroically told her to instead save the life of Twilight, who had been forced to work for Lilith and had at the last moment sacrificed herself to help defeat Lilith. A wise move, as Twilight has the power to bring the dead back to life, and when she merged with Matrix she became the new Angel of Fire and healed Linda, restoring as much of Linda's "own powers" as she could (i.e. her Supergirl powers as seen at the beginning of the series, before the angelic powers appeared). So Linda is Supergirl in her own right, the duty of Earth-born Angel has been passed on to Twilight along with the wings of fire and remaining essence of Matrix. It appears that the spirit and power of Supergirl is wide enough to exist in both the superpowered person of Linda Danvers, and as a merged entity with Twilight. Confusing is an understatement!
Following the end of the "Quest for Supergirl" saga, yet another Supergirl appeared in issue #75. This is the original Kara from Krypton, and she caused quite a bit of confusion with her claims that she is the true Supergirl and cousin to Superman. Since Kara died in the Crisis on Infinite Earths and all memory of her was wiped from the remaining inhabitants of Earth (including Superman's), her appearance was a great mystery to the post-Crisis Supergirl (Linda Danvers). Kara was indeed who she claimed - Supergirl, Kal-El's cousin - detoured into the post-Crisis universe on her way to the pre-Crisis Earth. This bit of retroactive rewriting of past comics posits that the Supergirl we know from the Silver Age (known in DC continuity as "Earth-1"; Golden Age characters were said to inhabit "Earth-2") was diverted into our current continuity. The Silver Age world Kara was destined for is definitely not the one we know, as Linda Danvers discovers when she lives there for a while. It's like living in an idealized version of the 60's! No one swears, the villains are always easy to defeat, and everything's very, very clean. A utopia for comicbook characters, one in which Linda Danvers has a perfectly happy life in which she marries Superman (she refuses to be anyone's "secret weapon"!) and has a daughter named Ariella. At the end, however, she must return to her rightful universe, and Kara must return to her pre-destined place in history in a Silver Age world where she would become known as Linda Lee/Supergirl, with no memory of her time spent on our modern Earth.
The "Many Happy Returns" arc was intended by Peter David to kick-start a new direction for the comic which would feature the three Supergirls: Kara the original Supergirl, Linda Danvers taking on the mantle of Superwoman, and Power Girl. (Revealed by David in If Supergirl Had Continued). Who wouldn't have loved that? However the series was prematurely cancelled and David was forced to wrap up the story in issue 80, giving us a bittersweet ending to Linda's and Kara's story. Linda Danvers dropped the mantle of Supergirl and left Leesburg for parts unknown. In a farewell letter she wrote to Clark, she bequeathed her Supergirl mementos - and her beloved skateboard - and hinted that she might adopt a new identity. Supergirl's author moved onto a much darker series called Fallen Angel. The series stars a mysterious dark avenger named "Lee", who is unusually strong and supernaturally-abled. After much reader speculation that Lee was the disillusioned Linda Danvers living on in that little-known corner of the comicbook universe, Peter David revealed that Lee was not Danvers. However he introduced a new character named "Lin", Lee's predecessor, who is Linda Danvers in all but name (the series is now published by IDW, not DC Comics). See Wikipedia for further details on