Who Is Sensor Girl?
"Who Is Sensor Girl?" is a story arc that was published by DC Comics, and was presented in Legion of Super-Heroes (vol. 3) #14-27 (September 1985-October 1986). It was written by Paul Levitz, and pencilled primarily by Greg LaRocque, Larry Mahlstedt and Mike DeCarlo. The story arc includes the induction of five new members of the Legion of Super-Heroes, with the identity of one posing a major mystery.
Plot
With its three founders having announced their intention to resign from ACTIVE duty, the Legion of Super-Heroes holds its first major membership drive in years. Power Boy, Comet Queen, Mentalla, Energy Boy and Dev-Em are among the various candidates. Ultimately, five new members are voted in, including Tellus, Quislet, Cosmic Boy’s younger brother Magnetic Kid, and Legion of Substitute Heroes founder Polar Boy, who finally accepts the Legion’s long-standing offer of membership. The fifth new member is Sensor Girl. She is a masked woman who keeps her powers and identity secret, but is voted in based upon a recommendation from Saturn Girl, who states that she “has the best of reasons to deserve Legion membership.”
Over the new few weeks, Sensor Girl displays a variety of powers. She is aware of an explosion occurring miles away before any of her teammates, illuminates the darkness with infra-red light, and displays impressive prowess in hand-to-hand combat. She properly analyzes the glandular imbalance in one of her teammates, and is able to see and hear through walls. Brainiac 5, grieving the death of his longtime love Supergirl, begins to suspect that Sensor Girl might actually be Supergirl -- or a traitor in their midst. The mystery deepens when Brainiac 5 breaks into her quarters and discovers that she has been flying without using her Legion flight ring. Team leader Element Lad is reluctant to ask Sensor Girl to reveal her identity, as years earlier he was also admitted into the Legion on Saturn Girl’s recommendation alone. However, as teammates grow suspicious and internal conflict develops, he is forced to raise the subject with Sensor Girl. She responds by resigning from the team. As she leaves Legion Headquarters, Ultra Boy uses his penetra-vision to see through her mask, and is stunned when he discovers that her costume is empty.
Meanwhile, the Emerald Empress has reformed the Fatal Five, recruiting the Persuader (her former teammate) and Legion reject Mentalla, among others. The Legionnaires desperately search for Sensor Girl, worried that she might have accepted the Empress’ previous offer of alliance. Dawnstar tracks her to the cemetery planet Shanghalla, where the trail dissipates. Element Lad raises the subject of Sensor Girl’s qualifications with Saturn Girl. She reiterates that Sensor Girl deserves Legion membership, adding that “she was already a Legionnaire.” On the planet Stratus, the new Fatal Five attacks a small faction of Legionnaires. Sensor Girl arrives and leaps to the defense of the heroes, but she is overcome by the Empress, who exposes the mystery woman’s true identity: Projectra.
Brainiac 5 finally deduces Sensor Girl’s identity, which is confirmed by Saturn Girl. Projectra had travelled to Shanghalla to visit the tomb of her late husband Karate Kid, who tutored her in hand-to-hand combat. Her other seemingly endless abilities were the result of her illusion-casting powers, magically heightened by the spirits of her ancestors to include the ability to see through reality's illusions -- including those of size, distance, time and death. Desiring to return to the Legion in secret, she and Saturn Girl developed the Sensor Girl identity. Projectra and the other Legionnaires battle the Fatal Five, who soon realize that Mentalla is a mole in their ranks, and has not truly betrayed the Legion. The Empress murders Mentalla, but Sensor Girl is eventually able to single-handedly defeat both her and the remaining villains. Afterward, Projectra abdicates the throne of Orando. The Legion officially votes her into the Legion again as Sensor Girl, accepting her role in the death of Nemesis Kid as a case of self-defense.
Post-Zero Hour
In post-Zero Hour continuity, a snake-like non-humanoid named Sensor joins the team, possessing illusion-casting powers similar to those in Projectra’s original incarnation.
Post-Infinite Crisis
In the aftermath of the Infinite Crisis miniseries, most of the Legion's original continuity has been restored. Elements of the Sensor Girl mystery are once again part of Legion history. Sensor Girl's supposed connection to Supergirl is removed, as the Girl of Steel is not a member of this incarnation of the team.