Alan Moreland, retired financier, is compelled by a hypnotic floral arrangement to empty the contents of his safe. Across town, at the Drake Flower Shoppe, astronomer Ted Knight calls on the owner, Dinah Drake Lance. Dinner arrangements are made, with Lance giving Knight a flower to wear, as a reminder. Knight next pays a visit to the Park City Astronomical Observatory, where he wiles away the afternoon hours studying quasars. Suddenly, the stars vanish from Knight's view, as his ears begin ringing. Then, a hypnotic voice emanates from the flower in his buttonhole, detailing instructions for a cash drop-off. Knight, as Starman, rushes to intercept the criminals in the act. Starman observes the criminal gang from the trees, then brings his cosmic rod into play. The cosmic rod, however, has ceased functioning. With no other recourse left available to him, Starman leaps down from the trees and wades into the group of crooks. A brutal fist fight ensues, with Starman beating down all but one member of the gang. As Starman closes on the last man standing, a flower in the crook's buttonhole emits a series of high-pitched sounds that render the Astral Avenger unconscious. The criminals make off with the loot, reporting back to the mastermind behind the crime, Starman's old nemesis, the Mist.
Lance's husband, private investigator Larry Lance, has tracked the Mist's crime wave back to his wife's floral shop. Lance refuses to believe her flowers could have any connection to the crimes. Starman arrives, and details his own experience with the hypnotic talking flower Lance placed in his buttonhole. Lance goes to lock up her shop, but, upon her return seems to be under a hypnotic spell. Starman uses his cosmic rod to make the adjoining wall to Lance's office transparent. Then, Starman and Lance's husband spy on the girl, who gives instructions, into a bouquet of flowers, regarding the wealthy clients receiving the next day's floral arrangements. The communication with the Mist, however, goes both ways. Thus, from eavesdropping on Lance prior conversation with Starman, the Mist has gleaned the reason why his cosmic rod ceased functioning, earlier that evening. The Mist instructs one of his goons to record the motor noises of the observatory, as those sounds coupled with the ultra-high frequencies of his hypnotic flowers effectively jam the rod's ability to draw power from starlight. Starman reveals to Lance her role as the criminal mastemind's pawn. Enraged, Lance puts on her Black Canary costume, ending her long retirement from costumed crime fighting. With three potential crime scenes in the making, Starman, Black Canary and Larry Lance split up to cover each of the Mist's targets. Fearing that his cosmic rod will again cease functioning, Starman gives the Black Canary a newly designed miniature version of the rod, powered by quasars, to be used as a secret weapon against their foe.
Frieda Van Taller is instructed, by the Mist's hypnotic flowers, to leave her most valuable gems on her vanity, then leave her home. Then, the Mist's gang, rendered invisible by his inviso-solution, arrive through an open window to carry out the robbery. Entering through the same open window, the Black Canary removes a pellet of reddish powder from the amulet around her throat. Breaking open the pellet, she blows the powder into the room, revealing the invisible thieves. In short order, the Black Canary defeats the three crooks with her martial arts prowess. Across town, Starman thwarts the robbery, by helicopter, of the Yacht Club's charity receipts. Larry Lance, as instructed, only observes the third crime being committed, then follows the crooks back to their hidden lair. Lance contacts Starman and Black Canary, and reveals the location of the Mist's headquarters. Lance's communication, however, is picked up by the Mist's specially treated flora. Very quickly, Lance is located and subdued by the Mist's invisible henchmen.
Starman arrives on the scene first. The Mist's jamming frequency disables the cosmic rod, causing Starman to plummet to the ground. Crashing into a tool bench, the dazed hero is easily beaten down by the Mist's invisible henchmen. The Black Canary rushes in. Seeing Starman downed, the Black Canary immediately brings the quasar powered cosmic rod into play. The Black Canary takes out all of the Mist's invisible goons, while also destroying most of the Mist's delicate machinery. The Mist activates his only remaining defensive weapon, pellet shooting compressed air guns. Inexperienced in the use of the cosmic rod, the Black Canary's faulty shield allows enough of the pellet barrage to penetrate, rendering her unconscious. Starman, however, has recovered. With the Mist's devices destroyed, Starman's cosmic rod once again draws power from the stars. Projecting a protective bubble around the Black Canary, Starman beats down the rest of the Mist's goons, then takes down the Mist. With Lance released from captivity, and the criminals turned over to the authorities, Ted Knight is finally able to keep his dinner appointment with the Lances. Knight attempts to convince Lance to keep the miniature cosmic rod, but Lance refuses, believing that, as the Black Canary, she simply doesn't need it.