Tara needed to find someone to take care of Deanna while she was overseas for work. She knew she'd be gone for an extended period, so it needed to be someone she trusted.
Dee was adamant that she wanted to stay with Tom while her mother was gone. Mom knew of Dee's feelings and that her ulterior motives in the request, but could not discount Deanna's feelings or wishes.
Tara and Tom go back ten years and both held a secret that Dee didn't know yet. Only some of the secret comes out here, but enough that Dee is very surprised, but not deterred in her true feelings or her ultimate objective.
She'd met Tom during some ugly times in her life while he was living with four very beautiful gay women. There were special relationships in the house that Tara became part of temporarily. Once the crisis was over, she moved along, but still maintained her love for Tom.
Unfortunately, for both, it was an arm's length love, but that didn't discourage Deanna after she'd finally met him. Tara knew immediately that she had a problem.
Tara knew of Dee's devoted love for Tom, she'd known since Dee was eight. Dee was nearly sixteen when she had to leave and she knew that Dee could be very persuasive, but trusted Tom. She knew that in the end, he would do the right thing. She also knew what Dee wanted and that by leaving her, she'd be essentially giving her up.
There are many twists and turns in the love that Dee feels for Tom, and "friends" are walking in and out allowing both Tom and Dee to keep things amusing. When you add Tara to the mix, it gets very interesting indeed.
It took Dee two years to break him down, but break him down she did, and thus began a very tender love story while Dee and others were the full beneficiaries of Tom's extraordinary "Learning Experience".