Help me out with Lethal White..

[newname18]

... I started reading two weeks ago but have only had the time to read in tiny chunks due to my rather demanding baby boy, and I've missed some key bits I think?

I'm up to the bit where Robin is undercover in the Houses of Parliament. She is spying on someone- who and why? Who is Della? How do they link to the MP? And where does the psychotic man at the beginning come in to that?

Any answers appreciated I'm on my Kindle so not finding it easy to flick back through for answers

SPOILER (Just in case)

Della is a fellow MP, who is blind, her husband works for her. Their office is on the same corridor as the one Robin works in.

Billy, the psychotic man, does tie in, but quite a bit on in the book, so I don't want to give that away.