The Mode series is a quartet of novels by Piers Anthony. Like many of Anthony's other fictional works, it explores many themes and ideas. This series has themes of violence, the abuse of power, sexism and male dominance, gender roles, the environment, integrity and personal honor, sapient animal life, parallel and alternative evolution, space travel, alternate dimensions, paradox, obscure concepts in physics and mathematics, sexual assault and abuse, child and adolescent sexuality, and suicide.

Though initially marketed as fantasy, the Mode series is similar to the Incarnations of Immortality and the Apprentice Adept series, blending fantasy and science fiction.

Mode, in the series, is another word for "reality" or "universe." The philosophy is heavily inspired by eastern philosophies. The Virtual Mode is like a three-dimensional plane that cuts across many realities. It requires five points, represented both by anchor modes and anchor persons, to hold it in place. When someone hears the call of the Virtual Mode, he may reach out with his mind and set his anchor point, thereby becoming an anchor person. When two or more persons act in tandem to attach the Virtual Mode, both will become anchors. Only anchor persons may travel freely on the Virtual Mode; other travelers must remain in contact with the anchors lest they become lost in one of the non-anchor modes. In addition, only objects from anchor modes may be transported on the Virtual Mode; any other materials will remain in their mode of origin. Once the anchor point is fixed, mode travelers may step in and out of the Virtual Mode at that point, thereby being able to interact fully in the anchor reality. Anchor persons may only travel ten feet across non-anchor modes before crossing the border into the next reality. Though each mode is only ten feet deep, it is infinitely wide; anchor persons may travel as far as they like to the side as long as they don't cross the border. Each reality is like an individual sheet of mica, and when each individual plane is placed next to others, together they form the whole Virtual Mode. Each mode has its own rules which determine which aspects of science and magic will work there.

Only the death or purposeful release of an anchor person can free an anchor point. When that happens, the Virtual Mode is unstable until another person invokes their anchor. Few people are able to sense the Virtual Mode; only those who can may become anchor persons. In the series, those who invoke the Virtual Mode are typically individuals who have some great need for change in, or escape from, their current situation that only access to the Virtual Mode will provide. In addition, the Chip that invokes the Virtual Mode has different settings which determine the realities that will be included in any given Virtual Mode. Though it can be set to include only modes populated by human beings, the Virtual Mode in the novels is set instead to include sapience of any type, including non-living beings such as machines.

Colene, who appears to be bright and popular at school, secretly flirts with suicide and cutting herself for emotional release. Her death wish prompts her to approach a strange man that she finds in a ditch on her way home from school, and her relationship with Darius begins.

Darius and Colene rapidly fall in love, but he regretfully leaves her when she cannot bring herself to accept that he is from a magical reality. After his departure, Colene realizes he was telling the truth, and, in despair, she prepares to commit suicide. Back in his own mode, Darius realizes that he loves Colene too much to give her up. He therefore uses a magical device called the Chip to create a Virtual Mode so he can travel back to Colene.

Colene quickly seizes the opportunity to become an anchor person and sets out along her side of the Virtual Mode. On her way, she befriends Seqiro, a telepathic stallion and, to Colene's joy and surprise, another anchor. As Sequiro joins her in traveling the Virtual Mode, she opens up to him and reveals the source of her depressive and suicidal nature; she had been raped at a party by several older boys but did not report the incident out of fear of humiliation and because she had become drunk during the party. The two make rapid progress towards Darius' mode until they are unexpectedly trapped in DoOon, home mode of the emperor Ddwng, who is the anchor for his world. Forced to suffer captivity thinly veiled as hospitality, Colene and Seqiro must wait for Darius to arrive.

Meanwhile, Darius has encountered another anchor—Provos, a strange older woman, while traveling toward Colene. Able to remember the future, she is able to help him avoid or defeat many hazards on the Virtual Mode. Eventually, they reach a series of beacons, which they follow to DoOon.