The era of the Old Republic is a dark and dangerous time, as Jedi Knights valiantly battle the Sith Lords and their ruthless armies. But the Sith have disturbing plans—and none more so than the fulfillment of Darth Scabrous's fanatical dream, which is about to become nightmarish reality.
Unlike those other Jedi sidelined to the Agricultural Corps—young Jedi whose abilities have not proved up to snuff—Hestizo Trace possesses one extraordinary Force talent: a gift with plants. Suddenly her quiet existence among greenhouse and garden specimens is violently destroyed by the arrival of an emissary from Darth Scabrous. For the rare black orchid that she has nurtured and bonded with is the final ingredient in an ancient Sith formula that promises to grant Darth Scabrous his greatest desire.
But at the heart of the formula is a never-before-seen virus that's worse than fatal—it doesn't just kill, it transforms. Now the rotting, ravenous dead are rising, driven by a bloodthirsty hunger for all things living—and commanded by a Sith Master with an insatiable lust for power and the ultimate prize: immortality . . . no matter the cost.
Darth Scabrous, leader of the Odacer-Faustin Sith Academy, secretly hires the Whiphid bounty hunter Tulkh to steal the Murakami orchid from the Jedi Agricultural Corps facility on the planet Marfa. When Tulkh steals the orchid, however, he finds that he cannot take it back to Scabrous alive without the plant's handler, Padawan Hestizo Trace. Taking them both back to the academy, the Sith Lord mixes the orchid in a strange device hooked up to Sith apprentice Wim Nickter, who had been taken by Scabrous for his purposes. Nickter dies, but comes back as a zombie. His infection spreads throughout the academy in a single night, infecting even Scabrous himself. Hestizo finds herself trapped with Tulkh in trying to fight off hordes of zombies. Meanwhile, Scabrous preoccupies himself with finding a way to become immortal without the side effect of becoming a mindless monster. To do so, he infects the Neti librarian, Dail'Liss, and commands him to lure Hestizo to the library by mimicking the voice of the orchid, still alive amidst the infection known as the Sickness. The plan works after she and Tulkh part ways. Scabrous straps Hestizo to a sacrificial altar to cut out her heart with a traditional Sith sword. By consuming Hestizo's heart, Scabrous hopes to negate the decaying effects of the Sickness while retaining his eternal life.
Meanwhile, as Tulkh does his best to survive and find a way off of Odacer-Faustin himself, he comes into contact with Scabrous's personal HK-series assassin droid, programmed as a protocol droid, and modifies it to combat the zombies. Together, the two of them make it back towards Tulkh's ship, the Mirocaw, where they find a stowaway named Pergus Frode on board. Frode was the mechanic for the previous crew hired by Scabrous for the purpose of retrieving a black orchid; when that crew was killed by Scabrous for their failure, Frode had been stranded, left to survive the zombie epidemic.
Back at the base of the Sith library, Hestizo frees herself from Scabrous's sacrifice. Before Scabrous can kill her, Hestizo's brother, Rojo, arrives and duels the Sith Lord. Scabrous kills Rojo, but Hestizo kills Scabrous by telepathically convincing the orchid to sprout itself outward from his head, severely weakening him. She then finishes off Scabrous, now a complete zombie, with his own Sith sword. Hestizo escapes infection from the remaining Sith zombies when the Mirocaw, piloted by Pergus Frode, flies in to save her. The ship evades Scabrous's perimeter defenses long enough to reach the roof of Scabrous's personal tower. There, the HK manipulates the perimeter defenses to destroy the tower instead of the Mirocaw as zombies invade the roof and the ship flies away. The tower is destroyed, along with all the remaining zombies and the droid.
However, Hestizo finds that the Sickness still has a chance of infecting the rest of the galaxy - Tulkh was infected back on the planet when an infected tauntaun's spittle dribbled into his eye. Knowing that his time is limited, Tulkh asks Hestizo to open up the wall he chained himself to so that he will be blown out into the vacuum of space. Before she can do so, however, an infected apprentice from the academy, Rance Lussk, attacks, but Hestizo avoids his attack and sends both Tulkh and Lussk out into space. She seals the room that they were blown out of, and rests assured that the Sickness is over.
Hestizo returns to Marfa, where a new black orchid is waiting for her care. However, she instead decides to return to Coruscant where she can resume her proper Jedi studies.
The first draft of the novel contained a character named Middish Sunblade, modeled after Holden Caulfield, but he was removed in a later draft. According to Schreiber, this was because Sunblade "was whiny and nobody could stand him."
The character of Rojo Trace is based on Liam Neeson's character from Taken, and even utters a line almost identical to that character near the beginning of his story arc.
The snow planet Odacer-Faustin where the Sith Academy exists is based on a combination of Hoth and the snowy terrain of The Shining.
Toward the end of the novel, Hestizo Trace mentions returning to the Jedi Temple on Coruscant in order to further her education and training. This is an error, as the Temple was destroyed during the Sacking of Coruscant, eight years before the setting of the novel.
Red Harvest was originally called Black Orchid. It was a reference to the Murakami orchid at the bloody heart of the "Sickness". The final title Red Harvest is a nod to Return of the Jedis code name Blue Harvest: Horror Beyond Imagination.
For the German edition published by Blanvalet, the novel was re-titled Darth Scabrous.