The Intruder by Maurice Maeterlinck is a play that explores the theme of death. In fact, the titular intruder is Death itself. This is hinted in the scene when the family members hear someone sharpening a scythe, which is associated with Death or the Grim Reaper. The other main character of the story is the blind grandfather. He is the only one in the family who is psychically aware of the Grim Reaper. Each member of the family becomes paranoid to an extent, none more concerned with the possible intruder than the grandfather himself. Since the play ends with the impact of death—in the form of the mother succumbing to her illness—it is clear that Death personified has entered the home. Death is treated with the same level of fear and suspicion as an unwanted visitor, emphasized as an unseen being that can lurk eerily in the shadows undetected. It is Death who holds the power of an intruder to disrupt the family’s lives forever.

A prominent theme in The Intruders surrounds the dynamics of a family. The mother is ill and has been sick since giving birth to her youngest child. The newborn baby has not made a sound since his birth; in fact, the child only wails when the mother is discovered to be dead. The grandfather believes the child has been affected due to the fact that his daughter had an incestuous relationship with her cousin. This shows the insularity of the family which is contrasted with the exclusion of the grandfather's opinions regarding the unseen intruder. The family does not merely get along smoothly or value each other’s opinions readily. They bicker, invalidate each other’s beliefs, and even talk about the grandfather right in front of him after he falls asleep. The father and uncle are frustrated, too, that the sister (who is a nun) has not arrived. Her lateness, and eventual no-show, adds tension to the dynamic. The action is propelled primarily by the members of the family onstage: no one comes and goes unless to check on the baby, and the majority of details surrounding the “intruder” are imagined or exaggerated by the paranoid family.

One substantial theme of the play is duality. This is seen throughout the story in several instances: light and darkness; noise and silence; male and female; life and death. The latter example of duality—life and death—become a symbiosis, which is symbolized by the crying of the newborn baby as the mother died. Another important duality is that of the grandfather. He is blind, yet speaks frequently throughout the play about sight. He asks his granddaughters to describe what they see, wondering if there is anyone by the road or by the pond. He wakes up suddenly, convinced someone is standing in the glass door that he cannot see due to his visual impairment. He laments that he has not “seen” his daughter, that even though he saw her the day prior he has not seen her for a long while. He claims that the lamp appears to be unsteadily flickering when, of course, he has no way of knowing this. It is as if he can see beyond the natural world; he bears witness to what those with traditional sight cannot.