Existing studies, in Nigeria, have explored the interplay of physical and psychological diseases with a central focus on different psychiatric conditions as well as their social triggers. This article examines ambition as a major intensifier of neurotic and psychotic episodes in Femi Osofisan’s play, A Restless Run of Locusts. Freud’s psychoanalytic theory is adopted to account for the mental states of the characters, as manifested in their moods, conducts, gait, physical dispositions and utterances. The play is subjected to a critical analysis to reveal some psychiatric symptoms elicited by grave ambition, as exhibited by its protagonist and other characters featured in it. Besides a close reading of the primary text, secondary materials on the field of psychiatry and literature give insights to the study. The play reveals different psychotic and neurotic features which emerge from the fierce greed and ambition of the protagonist in his craving for political positions and privileges. Through verbal and behavioural displays, Osofisan’s protagonist undergoes a gradual descent into mental derangement, from neuroses to psychoses.