If the cacophony on stage during the Vineyard Theatre’s “Dot” even remotely characterizes the “noise” inside Dotty’s head, it is easy to understand the severity of her Alzheimer’s disease and just how far it has progressed. Colman Domingo’s new play tackles the horrific details of one family’s struggle to cope with the deterioration of their mother and how her mental decline counterpoints each member’s personal struggle with reality and its disintegration.

Dotty Shealy (Marjorie Johnson) lives in the Philadelphia home she shared with her husband and in which she raised her two daughters and her son. Her daughter Shelly (Sharon Washington) has assumed the burden of caring for Dotty and is completely overwhelmed with that undertaking. The play opens two days before Christmas as Shelly and Dotty chat with former neighbor and family friend Jackie (Finnerty Steeves) who has returned from New York to borrow some linens and share that she is pregnant and about to be a single mother. Shelly and Dotty also await the arrival of Shelly’s sister Averie (Libya V. Pugh) and her brother Donnie (Stephen Conrad Moore) and his husband Adam (Colin Hanlon).

Once everyone arrives, the bickering about what to do with Dotty begins as she seems to fade away before their eyes. She forgets Shelly went to buy the Christmas tree, what medications she is supposed to be taking, and what time it is. Moments of lucidity collide with long stretches of forgetfulness and her disease becomes ever more present. The first act of “Dot” is strong and successfully introduces each character, delineates their specific conflicts, and paves the way for discovering more about Dotty and her illness. Unfortunately, this expectation remains unsatisfied.

In the second act of Mr. Colman’s play, Dotty’s important story gets sidelined by the subplots Mr. Domingo decides to place center stage. Despite the family’s insistence on calling a meeting to discuss Dotty’s condition and care and “getting her what she needs,” the only conflicts explored are those of the family – nuclear and extended including Dotty’s caregiver Fidel. Each of these stories is interesting and engaging but none have anything to do with Dotty. And why Jackie is even in the story is baffling. The ensemble cast bravely moves through the script and does the best it can to honor the intentions of Mr. Colman’s script. Unfortunately, the script’s weakness overshadows the collective craft of the cast. Dotty’s dementia becomes lost in her extended family’s delirium.

There are puzzling choices made by the playwright and director Susan Stroman that unfortunately detract from the power the play should and could have. For example, although there is no indication in the first act that Dotty is fully aware of her diagnosis, in the second act the plot hatched with Fidel to shame her family into understanding her condition is played out in an unfortunate comedic fashion. Fidel describes the exercise as “the virtual dementia experience” he and Dotty found online. Adam suggests they should have gotten “the actual kit” and not assembled the parts themselves.

And the choice to focus on a myriad of family issues leaves Dotty’s decline a mere side issue. The play tries to be about her memories and her unreliable mind but it is more about marriage equality, unwanted pregnancy, immigration reform, and sibling rivalry. The second act regrettably is more fractured than Dotty’s mental faculties and leaves the audience wanting more about Dotty.