Cathy doesn't want to be the one who is always responsible and in control, especially now that she has been diagnosed with a terminal case of melanoma. That's why she kicked Paul out of the house as she literally wants to be the one in their twosome who is seen as the person who freely spills wine on the sofa without caring, instead of that person always being Paul. That's why she's decided that she wants a pool built in their postage stamp sized yard, so that she can teach Adam how to do the banana split dive like she did when she was his age. That's why she feels that she can give Adam a taste of his own medicine by treating him as thoughtlessly as he seems to treat her, all in an effort to make a point. That's why she feels that she can be blunt instead of being politically correct to her student Andrea about the combination of her wisecracking and her weight. That's why she decides that she doesn't need to be cordial anymore to their crotchety neighbor, whose name she doesn't even know after living next to her for five years. And that's why she tries to reach out to Sean despite Sean abhorring everything about what he sees as Cathy's chosen bourgeois lifestyle. Regardless of these changes, Cathy isn't yet ready to tell anyone, let alone her family - Paul, Adam or Sean - that she is dying.

Cathy learns from Dr. Mauer that she probably has at least a year to live if not longer, which gives her some perspective of how much time she has left to do the things she wants. Chief among these is spending time with Adam. So instead of allowing him to go away to soccer camp for six weeks over the summer, she decides unilaterally for him to stay home over the summer so that they can spend time together. Cathy's actions seem crazy to Adam and Paul, both who still don't know about her medical diagnosis. Regardless, Cathy goes to extreme lengths to get what she wants. Dr. Mauer's time estimate also makes Cathy examine her body image, which she is doing truly for the first time in her life. What she sees surprises her. Meanwhile, Paul still isn't sure why Cathy won't let him come home and thus suggests they attend marriage counseling. Cathy treats the sessions with the knowledge of what she knows is the problem in relation to her health situation without divulging anything about the melanoma.

Cathy still isn't feeling like she can let Paul back in the house or in her life. Adam is still angry with her and avoids her at all cost. And Sean still believes that Cathy is too uptight with who to hang out. So at this crucial time in her life, Cathy is feeling all alone, that is except for Thomas, Marlene's beagle, who always seems to be following her around. Her attempts at bringing Sean - and his girlfriend Daphne - and Adam and Andrea as meaningful parts of her life don't end up quite the way she envisions. As such, Cathy decides to attend a cancer support group. But those in the group end up being way too happy and upbeat for her liking, they seeing their cancer as it is a gift. Regardless, the support group appoints itself as her "Team Cathy" whether she likes it or not, as they believe that she really does need someone in her life for support. She has to decide if Paul is a better option, he who really does want to move back in. Thomas may find Cathy an unexpected substitute.

Since she knows she won't reach retirement age, Cathy decides to withdraw all the funds from her retirement plan and do whatever she wants to with the money without a care. Among other things, she indulges on material goods such as an expensive bottle of champagne, which she shares with her new confidante, Marlene. But her biggest purchase is a red convertible sports car, which she can't drive since she doesn't know how to drive a stick shift. Regardless, she decides to spend the day with her new toy and Dr. Todd house hunting while pretending to be his older girlfriend. In the process, she liberates a lobster. That time with Dr. Todd shows her where her true future lies. Meanwhile, Paul, looking for something meaningful to do in his life while he's not at home, decides to head back to his school days and play rugby again. Sean, who has a toothache, refuses Cathy's offer of paying for a dental visit. Sean goes to extreme measures to deal with the tooth. And Marlene takes on the role of pretend grandmother to Adam, whether he likes it or not.

Adam is not talking to his mother again since she caught him watching porn, which was bad enough, but what made it worse was that she continued to watch it with him and analyzed why it wasn't realistic from a female's point of view. Cathy realizes what she did with Adam was wrong, but she still wants to make sure that at age fourteen he is not yet having sex, and that when he does that he can both talk to her about anything in that vein and that he treat the girl properly. As she deals with this issue, she is beginning to see physical beauty around her, which includes blue iris flowers, her own body and how best to show it off, and the sexy new muralist at the school named Lenny. Meanwhile, Paul has sustained a rugby injury which has him sidelined, but not in the eyes of "rugby tart", Tina. And the building in which Sean is living is scheduled for demolition. The only way he figures he can save his makeshift home is to play the game by acting like one of the masses who has conformed to society. He gets an unexpected hand in looking the part.

During the course of their continuing sexual relationship where they do it anywhere they can on unofficial breaks during the school day, Lenny notices a lump on Cathy's lower back side. Dr. Todd's diagnosis is that the cancer is showing itself, but that it does not necessarily mean that the cancer is getting worse. As it is purely a cosmetic issue, Cathy can choose to leave the lump or have it removed. She chooses the latter, and asks the only person who knows, Marlene, to pick her up after the surgery. The lump makes Marlene try to convince Cathy to tell her family about the cancer. It makes Cathy reevaluate her sexual relationship with Lenny and think about bringing her family back together, which includes not only Paul but also Sean. She figures that entering the family into a charity bathtub race, a race they used to always participate in and enjoy, but which Cathy stopped doing because of all the work involved on her end, is a good start. Some news from Paul, and Andrea finding out about Cathy and Lenny could bring Cathy's current plans crashing down around her.

After Marlene tells Cathy about the distant relationship she has with her own two daughters who Cathy didn't even know existed, Cathy decides she and Sean need to go visit their own father, who she feels they don't see often enough. Sean reluctantly goes as he openly dislikes their father, who didn't give him the time of day while he was growing up. Cathy, on the other hand, loves their father, as she was seen as the good one during her and Sean's childhood. This road trip ends up being one of discovery for both Cathy and Sean, those discoveries which affect the way she ultimately relates to her father, especially in light of the way he relates to her, which is the same way he's related to her, Sean and their now deceased mother for their entire lives. Meanwhile, Paul is at the house being Dad to Adam during Cathy's absence. But it isn't quite clear if there is an adult figure between the two.

It's Cathy's 43rd birthday. Coming to the realization that this birthday may be her last, she, on an impulse, takes Lenny up on his offer to accompany him to the Bahamas for the weekend. That plan is placed in jeopardy when Paul throws Cathy a surprise birthday party at the house. For her gift, Paul gives her Rebecca, her best friend from college who she hasn't seen in fifteen years after Rebecca, who was supposed to be Cathy's maid of honor, skipped the wedding in favor of hanging out with a man she just met. Time has not changed Rebecca's perspective on life. Another surprise or not so surprise attendee at the party is Lenny, who stops by the house to pick up Cathy to head to the airport. Lenny meeting Paul, the party itself, and Cathy reminiscing with Rebecca about their good old college days make both Cathy and Lenny reevaluate if their affair is such a good idea. Meanwhile, Sean does some catching up of his own with Rebecca. And Adam notices that something is not quite right with Marlene.

Paul discovers his wife's affair and demands a divorce.

Cathy's relationships with three people are on the outs. Following his decision to divorce Cathy, Paul turns to rugby tramp Tina for solace. Cathy has decided not to rekindle her friendship with Rebecca, due to Cathy believing that she has always put her sexual quest for men a priority over their friendship. It doesn't help that Sean is the latest in that long line of men. And Andrea drops out of Cathy's class, which Cathy learns is due in large part to knowing about her affair with Lenny, and Andrea's own attraction to him. Of those three relationships, Andrea's is the one Cathy tries to mend by helping her with her drug addicted mother, who has long been widowed when her husband was killed while he was committing a robbery. As Cathy finds out more about Andrea's life, Cathy turns to God, with a little advice from Marlene, to get through not only to Andrea, but Rebecca and Paul as well.

Now that Paul knows about Cathy's melanoma, he wants to help her in any way he can, including investigating alternate treatments. He is also still trying to get over the fact that he lost three months in trying to help her, three months in her probably shortened life. Cathy tries to explain to him why she didn't didn't tell him sooner. Paul, in dealing with the spouse of someone who died of cancer, begins to move closer to Cathy's way of thinking. Meanwhile, Rebecca tells Sean that she is moving to Minneapolis, but doesn't quite get the reaction she wanted. In a girls' bonding session, Marlene, Cathy and Rebecca go out for lunch to an unusual locale, an incident at which makes Cathy believe that Paul's thoughts about dealing with her illness aren't completely wrong. And Cathy learns about Marlene's Alzheimer's.

In an effort to be supportive of Cathy's decision and to find out more about it, Dr. Todd accompanies Cathy to Canada for her bee sting therapy. As open as he tries to be, Dr. Todd just can't get around how quackish the whole therapy seems. After the treatment, Cathy too believes that the "Bee Man" is a lunatic, but is glad she made the decision to take a chance. As their trip progresses, many revelations about Dr. Todd's professional and personal life become known to Cathy, which explains why he seems so protective about Cathy and why he wanted to come on this trip. Before she left Minneapolis, Cathy found out that Adam is seeing a girl named Mia, who, if she is indeed his girlfriend, would be his first. Cathy takes an extreme but nonetheless effective measure to ensure that things go well for Mia and Adam's possible relationship, despite the less than helpful advice he receives from his Uncle Sean. And an incident between Marlene, Adam, and Paul makes Marlene take decisive action.

Following Marlene's death, Cathy learns Marlene left her house. At first she's willing to let her daughters have it till she learns what their plans are. Dr. Miller wants her to try a different treatment which is risky. And she learns that Sean and Rebecca are expecting a baby.