the next deduction was the crucial one ; and depending on how clearly esther was thinking at the time and on how much her mind was able to admit to itself , she would have realised something somewhere between at the very least , that in having this letter in her flat meant that her tutor , stella had something to do with her family ; and at most , that stella had somehow been , in a previous existence , nothing less than her grandfathers wife , her fathers mother , her own grandmother .