Season synopsis
Contains spoilers for this season and earlier seasons.
Charlie’s relationship with Chelsea grows more serious when she asks him to spend a night at her apartment. The relationship tests Charlie's habits as she pushes for more consideration and he awkwardly adjusts to sharing his time and space. Elsewhere, Herb and Judith's marriage falters; Alan sleeps with Judith after she throws Herb out, then learns she is pregnant and worries the baby may be his. Herb returns to Judith, leaving Alan with the uncertainty while the household waits for the birth. Alan also grows close to his receptionist Melissa again, though an ill-advised attempt to live with her and her mother sends him back to Charlie's house.
Charlie tells Chelsea he loves her first, and her initial answer is simply, “Thank you.” He tries to force a matching declaration by proposing; Chelsea says she loves him but is not ready to marry again, and Charlie later calls himself “kind of engaged” while admitting she did not exactly say yes. They continue together, and she moves into the Malibu house late in the season, where Alan's friendship with her gives Charlie an excuse to delegate activities he dislikes. In the finale, Mia's return unsettles Charlie's commitment to Chelsea. Judith and Herb arrive at Charlie's house to pick up Jake, but Judith's labor begins there and the family rushes her to the hospital; Herb breaks his leg in the scramble. Judith gives birth to a girl, with paternity left uncertain, while Alan reconnects with Melissa at the hospital. At the coffee shop, Charlie tells Chelsea the hospital visit made him realize he would not mind having a child; after she leaves, Mia approaches him, leaving their next move unresolved.