I am ambivalent still about Mejia’s Leave No Trace, an intriguing mystery about a father and son, Josiah and Lucas Blackthorn, who disappear into Minnesota’s Boundary Waters without a trace. Ten years later, the nearly feral Lucas, now 19, reappears.

Uncommunicative, Lucas is placed in a psychiatric facility. The administration of the facility assigns Maya Stark, an assistant language therapist, to the silent Lucas, hoping for success where others have failed. Meeting the patient on his own terms, Maya refuses to be intimidated, eventually breaking through his resistance and gaining his trust. At 23, Maya has her own troubled history, haunted by a mother at odds with the demands of the world and her desire to stay in it. Her struggle has brought Maya to the institution, where she has found her career.

The early chapters present Maya and Lucas in an institutional setting, their encounters tightly controlled for optimum results, the return of the patient to a productive life in society. But the core of the story is more obscure, certainly found in the wilderness as lived by a father and son. Maya’s own grief is made more poignant in scenes from her childhood. Like Lucas, she thrives best in the environment beyond the walls of her work and Lucas’s confinement, the Boundary Waters a place of solace precious to both. When the drama segues from the institution to the outdoors, the author seems more sure-footed, more in touch with the emotional terrain of her two protagonists. The wilderness becomes another character, a longed-for place of safety and purpose.

Unfortunately, the scenes in the institution, while accurately portraying the limited dimensions of therapist and patient, create some improbable situations. Here the story seems more contrived in order to move the plot forward. Mejia has the right instincts, her talent more visible when unleashed in a freer environment, a few plot twists delivering an emotional denouement in the Boundary Waters, where nature provides the backdrop for a final resolution. When the action is set in the broad landscape of Minnesota, Leave No Trace comes to life, free of complications.