When Colonel Brandon tells his story to Elinor in Ch.31, he relates how his first care, upon returning from the East Indies, was to seek for her and that he spent six months in a fruitless search. I always wonder, when I read that, what he hoped to find or to do when he did find her?
Of course he would want to see how she fared following her shocking divorce, and of course he still had regard for her. Had he found her in health, he could not have married her himself, since she had been divorced from his brother. But, he still had feelings for her.
Looking for his ward Eliza must have been like the most horrible kind of deja vu for him. As with her mother, he searched for her for many months and finally gave up hope of finding her. She, too, had been seduced and abandoned by her seducer. Young Eliza was also left in distressed circumstances financially. And she, too, was left with a child by her seducer.
Colonel Brandon seems tortured by guilt over this. "Such has been the unhappy resemblance between the fate of mother and daughter! and so imperfectly have I discharged my trust!"
Surely he cannot blame himself for what happened to the mother. Perhaps he should have asked more questions about the trip to Bath, but I don't think he needs to blame himself for her daugther either.