Renowned psychiatrist Dr. Madeline Wyle is enlisted to treat seven-year-old Sophie Lewin, who was found on the side of the road hours after disappearing. Physically unharmed, but traumatized by the incident, Sophie's memories of that day remain locked inside her mind. The police have no leads. But as Sophie's parents John and Cynthia remain determined to get answers, strange details emerge under Dr. Wyle's care.

The police have a break in the case. As her treatment of Sophie continues, Maddie wonders if there is any truth to Sophie's fantastical memories. Maddie's commitment to her work takes a toll on her personal life as her teenage daughter Alex struggles with her recent move to Colorado. Maddie receives an unsettling call from her former lover and current hospital chairman, Henry Schulman. Cynthia arrives at Maddie's office with stunning news.

A mystifying event at the police station leads Maddie to believe that Sophie is undergoing cognitive changes. She seems to be transmitting otherworldly messages. A battery of neurological tests reveals surprising information about Sophie's brain. When Maddie visits Donny Kieber, who has recently been admitted to the psych ward of a nearby hospital, she makes an astonishing discovery.

Following a terrifying incident at their home, John and Cynthia are plunged deeper into their struggle to understand what is happening to Sophie. Maddie draws further parallels between Sophie and Donny Kieber. Maddie is forced to make a decision about her future with her daughter. A stranger named Rosa Flores is led to Maddie by ‘messengers,’ leaving Maddie’s pursuit for the truth suddenly thrown into a new direction.

Maddie and Rosa believe that they were meant to be connected, but they don’t know why. Rosa claims that whatever came for her is not of this earth. Determined to escape an abusive relationship and give her young son a better life in America, she is awakened to new feelings of power. As Maddie’s conviction grows about the connections between Rosa, Kieber, and Sophie, she makes a decision that puts her career in jeopardy.

Schulman issues a stern warning. Maddie is no longer permitted to treat Sophie Lewin. Maddie witnesses a violent confrontation between Rosa and her former boyfriend, but the moment takes an unlikely turn as Rosa’s powers grow. Maddie opens her home to Rosa and her son. Their bonds deepen. When Maddie visits Kieber at his home, she discovers that his mind is shattered. She tries to avert a harrowing incident.

Maddie’s esteemed career spirals. Under the scrutiny of an executive committee, she confronts the possibility that her clinic at the hospital could be shut down. As Rosa’s powers continue to develop, Maddie’s faith in her work is restored. An unexpected call from John Lewin leads to a fateful reunion with Sophie who has undergone an extraordinary transformation. Maddie considers the possibility that her life was meant to embark on this new journey.

When a DNA test reveals a profound revelation, Maddie grapples with the enormity of what she is pursuing. As she reconsiders her future, she receives surprising news from Schulman. Maddie finds solace in her love for Alex. A poignant call leads to a promise that Maddie vows to keep. Maddie arrives in Boston to accept the prestigious APA Humanitarian Award. An encounter with astrobiologist Lester Padgett leads to a seismic discovery, sending Maddie’s life into sudden uncertainty as the future of humankind hangs in the balance.