One of the twins happily asks John if Linda is dead. What does John do to the child?

After a date with Lenina that ends with John shoving her and forcing her to hide in a bathroom, John is notified by phone that his mother has overdosed on soma. Soma is a drug that people take every day, as encouraged by the World Controllers. This tragedy marks the end of Linda and John's enjoyment of the decadent world they find themselves in. When John arrives at the hospital, he is horrified to find his mother in a soma-stupor. It becomes clear that she is dying and he collapses to grieve at her bedside, recalling his childhood memories of her. This visceral reaction causes the nurses in the ward to believe that John has gone mad and worry that he will disturb a group of Delta twins who are there on a death tour. The children observe John's grief with distant curiosity before coming into the room to disturb him.
As John continues to cry over his mother's near-lifeless body, the children crowd around him to observe her death as if it is a spectacle for their entertainment. John is repulsed by the fact that they are eating eclairs, seemingly unaffected by the death and suffering that surrounds them. This is, in fact, the purpose of the death training that is used to condition the fear of death out of all citizens from a young age. One of the twins remarks that he thinks Linda is fat, which offends an already unstable John. Adding to his anger, Linda talks about Popé in her sleep. When one of the twins casually asks, "Is she dead?" after Linda has been silent for a while, John shoves him to the ground in a violent display that further shocks everyone in the ward. John's reaction is the result of all the anger that began accumulating on his date with Lenina. In a literary sense, it is the culmination of his growing distaste for society and its decadence as well as the apathy it instills. The child is merely a scapegoat for John's disgust with society in general, a construct he feels powerless to overcome.