Tabby is John's mother. As far as we can tell, she's kind of a babe. Owen is a little bit in love with her from the get-go, but it isn't just Owen who thinks she's great. Everyone seems to love Tabby. She's the kind of person who puts everyone at ease. She's a doting mom, a dutiful daughter, and a loving wife. As if her actions weren't enough to make people fall in love (or at least in sincere like) with her, she's also beautiful. Tabby accents her lovely figure by making her own clothes on her dressmaker's dummy. She expertly copies fashionable clothes that she borrows from high-end stores during her weekly trips to Boston, where she gets voice lessons on Thursday mornings.
One of the most important details about Tabby is also one that we get in the first paragraph of the book: Tabby dies in a freak accident when Owen hits a foul ball that hits her in the temple. Her death affects everyone. Not only does it change John's life forever, but it also transforms the way that Owen regards himself and his role in the world. Owen becomes convinced that he is God's instrument, and he sees Tabby's death as evidence for that assumption. Tabby's death is significant to John in a lot of ways, too – we mean, the death of a parent is a traumatic enough event in itself, but, when Tabby dies, a lot of John's questions about himself go unanswered. The big issue is that John was born out of wedlock, but he doesn't know who his real father is. When Tabby dies, John feels incredibly resentful that she died before ever revealing his father's identity.
As time progresses and John gets older, he finds out all kinds of secrets about his mom that make him question whether he ever really knew her at all. We learn that Tabby has two lives: there's Tabby the homebody who loves her son and takes care of him, and then there's The Lady in Red, the glamorous singer in the city.