Jack McCall is a charming literary agent who skillfully employs his gift of gab to secure various book deals, often bending the truth along the way. His life takes a bizarre turn when he attempts to land a deal with Dr. Sinja, a New Age self-help guru. Dr. Sinja sees through Jack's dishonesty and strikes a deal, but to Jack’s shock, he delivers a mere five-page book. That evening, a mystical Bodhi tree inexplicably appears in Jack's backyard.
When Dr. Sinja visits, they discover a peculiar curse: for every word Jack utters, a leaf falls from the tree. Once the tree has lost all its leaves, both it and Jack will meet their demise. To his horror, Jack realizes that even his written words count towards this limit, and any harm that comes to the tree directly affects him. If Jack attempts to cut it down, he suffers an axe wound; when squirrels scurry up the branches, he feels a tickling sensation, and if the gardener tries to poison it, Jack gets high from the fumes.
As Jack grapples with his new reality, he finds that communication becomes a challenge filled with misunderstandings. His struggles lead to significant consequences: he loses two important book deals, his job, and ultimately, his wife Caroline. She leaves him, misunderstanding his sudden silence as a lack of love. Even as Jack attempts to explain the bizarre situation, she dismisses his claims. Only his assistant, Aaron Wiseberger, believes him and keeps track of the remaining leaves.
Desperate to break the curse, Jack tries to improve his character by helping the homeless and donating to charity, but these efforts prove futile. In a drunken stupor, he sings excessively, causing the tree to shed more leaves. It is only when Aaron physically restrains him that Jack gains a moment of silence.
As the tree's leaves dwindle, Jack must face Dr. Sinja for guidance on how to lift the curse. The guru advises Jack to find peace in all his relationships. With just one branch left, he attempts to mend things with Caroline, but she is still wary. A visit to his mother, Annie, who suffers from dementia, reveals the need to forgive his estranged father for abandoning the family during Jack's childhood. Realizing that this relationship requires healing, Jack visits his father's grave and expends his last leaves by saying, > "I forgive you."
In a dramatic twist, Jack has a heart attack during a storm and appears to die. However, he answers the subsequent ring of his cellphone — it’s Aaron calling, revealing that magically, the tree's leaves have returned, and Jack can speak freely again.
Reunited with Caroline, Jack buys the family-friendly home she desired, with the Bodhi tree now planted in the front yard. While Jack does not regain his previous job (Aaron has taken over his position), he channels his experience into a new book titled A Thousand Words, with Aaron securing the publishing deal. Ironically, Aaron's new promotion seems to mimic the old Jack’s behavior, leading him to acquire his own smaller Bodhi tree in the office.
