Adventure Comics, Vol. 1 #407 (1971)

Suspicion Confirmed!
Linda Danvers is lying in the waiting room of the emergency ward of an hospital after walking in and out of a burning building. She is lucky enough to slip away before someone can examine her and discover she is Supergirl. The next morning she walks into work to find a new mystery: a man called Mr. Renard has come to KSF-TV and tells the news crew that he is reopening a theater supposedly haunted by the ghosts of an old film star and the leading lady he murdered. He thinks some person of flesh and blood is behind those haunts and hopes the modern equipment of the news crew can find the perpetrator in exchange for the scoop of the history. The crew spends two nights there trying to check things out, resulting in Johnny Drew and Nasthalthia Luthor getting kidnapped by a ghoulish figure. Kara feels mortified because she didn't dare save Johnny out of fear to reveal her secret identity. She decides to act when the strange being kidnaps Nasty, but her powers are still acting out and she is unable to rescue them. And because she was filmed as wearing a new costume, the police thinks "the crazy red and blue costume is in league with the creature that is behind all this".So in addition to blame herself for her early inaction and her failure, Kara is now angry. Her boss Geoff also blames himself and thinks it is his duty to rescue his employees. He intends to investigate the place alone and armed with a loaded rifle, and warns Linda if she warns the police, she is fired. Linda warns the police anyway and they stop Geoff. Even so, Linda feels conflicted. She has to rescue Johnny and Nasty. But what if she slips up and Nasty manage to prove she is Supergirl? Still she resolves she has to rescue them, no matter what. She let Johnny go to protect her secret identity, and blame is eating away at her. Her secret isn't worth one innocent life. That night Supergirl suits up and investigate the old theater alone. She discovers the "haunting" has been arranged by Starfire, who survived their latest confrontation.[2] She heard Supergirl was operating on the West Coast and set up a trap. Starfire captures Supergirl and after confirming the Girl of Steel is temporarily depowered, tries to dissolve her in an acid bath. Nonetheless, Supergirl is vulnerable, but her Kryptonian costume is still indestructible. Supergirl shields herself with her acid-proof costume and lets Starfire believe she has been killed. Then she emerges, rescues her friends and captures Starfire and her ghoulish minion. Supergirl turns them in, and then it is revealed Mr. Renard posed as the ghoulish kidnapper. As Renard claims he was blackmailed into it and Starfire complains about gutless and incompetent minions, Supergirl leaves.
Release Date: 1971