Donna Noble has been living the life: she's rich, she has a lovely husband and a new found career as the leading woman on her own temping agency. A big house. A summer house. A boat. Her mother is out of her hair. And she had a lovely wedding in a dress with pockets. Donna Noble has been living the life...
Except not. As times goes by, among those great things that mysterious lottery ticket gave her, her psych descends into depression. She's sad and she doesn't know why. Her husband can't bear to stay around her any longer. Her mother detaches herself to the extreme. The counselling board at the Temple-Noble Agency is slowly taking over.
Under very suspicious circumstances, Donna's Time Lord knowledge slowly starts to surface again, but not her memories. Her brain is filled with scientific data but detached from memories or history. She doesn't know how all that knowledge got inside her brain. All Donna knows is that she wants to use it for a good cause, but this may be far more difficult than she imagines - especially because having her Time Lord consciousness back wasn't a gift of any kind, but a manoeuvre to a greater (and darker) cause.
This is her last journey to remember.