Tyrone and Jamie continue their discussion about Edmund, who works for a local newspaper. Tyrone and Jamie have heard that some editors dislike Edmund, but they both acknowledge that he has a strong creative impulse that drives much of his plans. Tyrone and Jamie agree also that they are glad to have Mary back. They resolve to help her in any way possible, and they decide to keep the truth about Edmund's sickness from her, although they realize that they will not be able to do so if Edmund has to be committed to a sanatorium, a place where tuberculosis patients are treated. Tyrone and Jamie discuss Mary's health, and Tyrone seems to be fooling himself into thinking that Mary is healthier than she really is. Jamie mentions that he heard her walking around the spare bedroom the night before, which may be a sign that she is taking morphine again. Tyrone says that it was simply his snoring that induced her to leave; he accuses Jamie once again of always trying to find the worst in any given situation.
Between the lines, we begin to learn that Mary first became addicted to morphine 23 years earlier, just after giving birth to Edmund. The birth was particularly painful for her, and Tyrone hired a very cheap doctor to help ease her pain. The economical but incompetent doctor prescribed morphine to Mary, recognizing that it would solve her immediate pain but ignoring potential future side effects, such as addiction. Thus we see that Tyrone's stinginess (or prudence, as he would call it), has come up in the past, and it will be referred to many more times during the course of the play.
Mary enters just as Tyrone and Jamie are about to begin a new argument. Not wishing to upset her, they immediately cease and decide to go outside to trim the hedges. Mary asks what they were arguing about, and Jamie tells her that they were discussing Edmund's doctor, Doc Hardy. Mary says she knows that they are lying to her. The two stare at her again briefly before exiting, with Jamie telling her not to worry. Edmund then enters in the midst of a coughing fit and tells Mary that he feels ill. Mary begins to fuss over him, although Edmund tells her to worry about herself and not him. Mary tells Edmund that she hates the house in which they live because, "I've never felt it was my home." She puts up with it only because she usually goes along with whatever Tyrone wants. She criticizes Edmund and Jamie for "disgracing" themselves with loose women, so that at present no respectable girls will be seen with them. Mary announces her belief that Jamie and Edmund are always cruelly suspicious, and she thinks that they spy on her. She asks Edmund to "stop suspecting me," although she acknowledges that Edmund cannot trust her because she has broken many promises in the past. She thinks that the past is hard to forget because it is full of broken promises. The act ends with Edmund's exit. Mary sits alone, twitching nervously.
The latter part of Act I introduces us to the central conflict between Tyrone and Jamie. Tyrone believes that Jamie does not appreciate the value of money or the importance of hard work; Jamie has taken too much for granted. Jamie, on the other hand, thinks that his father is a penny-pincher, and he never shows his father any gratitude. Nevertheless, we see in this conflict an optimistic side of Tyrone, who maintains that his son still has the chance to become a great success. Their relationship and Tyrone's bitter disappointment suggests a thematic link between the two. Jamie is an example of the prodigal son who could have been like his father but instead chose to rebel. One of the strengths of the play is the presence of both Tyrone and Mary in their two children. In Act II, for instance, Edmund will criticize Jamie for thinking suspiciously by asking, "Can't you think anything but. . ." and cutting himself off before finishing. This is the same wording Tyrone uses in Act I to criticize Jamie's negative attitude. Similarly, we see towards the end of the act that Edmund and Mary share a common romantic vision. They dream of life in high society and comfortable living. Edmund concerns himself with Romantic authors and drunkenness while Mary entertains sublime fantasies about the role of the home and the success of her children. The character links come up several times throughout the play and affect the play's internal cohesion.
Jamie's comment that he "can't forget the past" introduces another central concern of the play: the role of the past in the events of the present. Each character in this play is at least partially controlled by his or her memories of the family's history. None of the men, for instance, are willing to believe Mary, because she has broken so many promises in the past. Both sons and Mary hold deep-seated grudges towards Tyrone for refusing to pay for a quality doctor for her, and the problems that created are still very much alive. Perhaps most importantly, Mary can never let go of the dreams she had as a young girl of being a professional pianist or a nun, both of which were destroyed when she got married. We see throughout the play her tendency to question whether she made the right decision, and this tendency fosters a resentment towards Tyrone, who she thinks was complicit in the destruction of her dreams. All these characters are haunted by all sorts of events from the past, none of which they can forget, as Jamie says. Thus, much like Mary's body as described at the beginning of the play, the family is slowly decaying because it is trapped by suspicions and problems resulting from mistakes made long ago which can neither be forgiven nor ignored.
We also see in this act Mary's specific idea of what a "home" is. More importantly, we learn that she does not feel like her house is any kind of a home, that she believes that she has never actually had a home with Tyrone, because they have lived their lives touring on the road. This is one of the manifestations of Mary's romantic vision of life that has been destroyed by the reality of her present situation. Unfortunately for her, Mary was never able to voice her concerns until too late in life; she always went along with Tyrone with little comment. Thus, we see that communication within the family is deeply flawed. This is also evident in Mary's continual refusal to admit the truth, and in the men's refusal to tell her the truth. We are left with a family who can easily argue and fight, but can never really communicate what they feel and want until it is too late. The play will move towards a resolution of this conflict towards the end of Act IV, when Jamie tells Edmund of his desire to see him fail, and when Mary and Tyrone discuss their old hopes.
Mary's concern over having a "home" introduces the concern over language into the play. Notice that the characters each command their own particular vocabulary that is highly politicized. Tyrone, for instance, is constantly calling his attitude towards money "prudent," while the other three call him "stingy." Likewise, Mary has a different definition of the word "home" than the three men. There is also a hesitancy on the part of all characters to say the word "consumption" in reference to Edmund. O'Neill's world is one in which language is politicized, where characters can claim language for themselves, and where other characters place a great stake in which particular words are used to describe which experiences.