Will Treaty has trained for years to be a Ranger. Now that he’s passed his Ranger trials, he travels to the Fief of Seacliff in the kingdom of Araluen for his first solo job, accompanied only by his horse, Tug. As Will approaches Seacliff, he discovers a bleeding border shepherd lying in the grass. He cleans and bandages the dog’s life-threatening wound and carries her with him.
In Seacliff’s village, he learns that John Buttle originally owned his adopted dog. Buttle is known as a dangerous man though no one has ever actually caught him committing a crime. Evidence suggests it was Buttle who injured his own dog and left her to die.
At Castle Seacliff he meets Baron Ergell, the man in charge of the fief, and Sir Norris, Battlemaster of Seacliff. As a Ranger, Will’s job is to monitor the fief and make sure the baron runs things according to the King of Araluen’s wishes. This includes the baron maintaining a well-trained force of knights and a tight security about the castle in order to preserve peace in the kingdom.
Ergell and Norris are pleasant men, but their style of leadership is slack, and Will is unsure of how to get them to improve their security. He hears rumors that the borders of the fief are unsafe, plagued with bandits who kidnap unwary people, and he is convinced that the Seacliff knights are not prepared to face any serious conflict.
His suspicions are put to the test when a group of Skandian raiders lands at Seacliff. Knowing the ill-preparedness of the castle’s fighting force, Will goes out to meet the Skandians and negotiate with them. Although there is a treaty preventing the Skandians from launching a full-scale war against Araluen, the treaty doesn’t prevent small parties from raiding areas. Will knows his best choice for avoiding conflict is offering the Skandians a warm welcome and a gift of provisions for their winter’s voyage back home.
A week after the Skandians’ arrival, Will’s childhood friend and former love interest Alyss comes to Will’s cabin on a surprise visit. Alyss is a diplomatic Courier in the service of Araluen, and she has come to tell Will that the Rangers are impressed with the way he handled the Skandian incident. They want to give him a special mission.
John Buttle approaches Will’s cabin and overhears their plans. He threatens to share the secret of Will’s reassignment and then attacks Will and Alyss. They fight and knock Buttle unconscious. Alyss considers killing Buttle to preserve their secrets, but Will gives the unconscious man to the Skandians so that they will make him a slave and take him with them on their voyage.
Will travels to the Gathering Ground, a meeting place for the Ranger Corps, and greets his old mentor, Halt, and the Ranger Corps Commandant, Crowley. Halt and Crowley send Will to Norgate Fief disguised as a common jongleur (traveling musician). Norgate has two castles: the main Castle of Norgate and a fortress in the north called Castle Macindaw.
Castle Macindaw is near a mountain pass, and it defends Norgate against invasions from the Scotti tribes to the north. Norgate’s current problem is that their ruler, Lord Syron, has been struck down by a painful and mysterious illness, supposedly inflicted on him by the legendary sorcerer Malkallam. This sorcerer has a vendetta against Lord Syron’s family. Locals have also been having spooky encounters, such as seeing vanishing lights in the forest and hearing unseen voices in the castle.
Will comes to Norgate and charms some nervous villagers with his singing. The locals relax enough to gossip with him about Norgate’s black magic problem. Grimsdell Wood conceals an apparition called the Night Warrior, a giant see-through figure of terrifying height, they say. Also, while Lord Syron has been struck down with an illness most people believe to be inflicted by the sorcerer Malkallam, many suspect Syron’s own son, Orman, of being the real sorcerer.
Orman is not a good leader, and his cousin, Keren, performs most of the duties of running Castle Macindaw. When Will arrives at the castle, still in his jongleur disguise, and receives unpleasant treatment from Orman and a warm, appreciative welcome from Keren, the differences between the two men are clear.
Will leaves the castle at night to explore Grimsdell Wood. He sees the disappearing colored lights and the Night Warrior, a giant ghostly warrior who warns him to run away. Will is terrified and unsure of what to do, but he gets help from Alyss, who arrives at Castle Macindaw under an alias.
Alyss and Will return to Grimsdell Wood the next day to search for clues. They learn that the disappearing lights were a trick designed to spook travelers, and Alyss discovers evidence that the Night Warrior is a projection caused by shining a powerful light behind a cutout figure of a knight. Alyss suggests that all these scary elements are designed to hide something important in the woods.
Will sends a messenger pigeon to Halt and Crowley to report on their findings. Halt and Crowley are concerned that Will and Alyss need backup. They dispatch a skilled knight named Horace to help them.
Will is shocked to see Buttle roaming around Castle Macindaw. He wants to warn Alyss that their enemy might be looking for her. On his way to find her, he is summoned to Orman’s quarters. Orman is in pain and says that Keren, who is also behind his father, Lord Syron's, illness, has poisoned him.
Orman says Keren has made a deal with the Scotti to the north to allow them to invade Norgate, so long as they give him Castle Macindaw. Orman asks Will to take him to visit the former healer Malcolm — often referred to as Malkallam because people believe he is the old sorcerer — to receive an antidote. As Will and Orman escape the castle, Keren’s men fire crossbows at them
In Grimsdell Wood, Buttle leads Keren’s men in pursuit of Orman and Will. The two evade discovery and find Malcolm’s large cottage in a clearing in the woods. As they approach, the clearing fills with about 30 people who suffer from deformities and bodily abnormalities, such as hunched backs or dwarfism.
Malcolm agrees to treat Orman, and Will discovers that Malcolm is a very clever healer who lost favor with the local villagers and went to live in the woods. The Night Warrior and other illusions are designed to keep people from disturbing his peace. His colleagues with physical deformities are people he has taken in because they were rejected by their own villages.
At Macindaw, Buttle recognizes Alyss as a Courier for the king. Keren imprisons her in a tower cell to keep her from revealing his traitorous plans. Keren gives her drugged water and attempts to hypnotize her into revealing Will’s true identity. Meanwhile, Will returns to Macindaw and climbs up the tower’s wall to rescue Alyss.
Keren returns to Alyss’ cell unexpectedly, and Will has to flee before he can help her, barely escaping to the forest on his horse before the castle guards attack him. He goes back to Malcolm’s cottage and vows that he will rescue Alyss even if he has to dismantle Castle Macindaw to do it.