5. Second To Last Of The Time Lords

The Face of Boe once told the Doctor that he wasn't alone. Soon afterwards, he finds the Master alive and well. The Face of Boe's statement could also have meant to reflect Jenny, River Song, the half-human 10th Doctor or even Doctor Donna. What if Boe actually meant Time Lady Romana? She went to E-Space during the Fourth Doctor's run and hasn't been seen in the series since. Perhaps she's regenerated a couple of times since then. She could return to this dimension and find her race extinct, except for the Doctor. How would the interaction with his former companion go?