A Death in Oxford

I'm happy. She's dead and I'm happy.

 Today I read ''A Death in Oxford'', CAMBRIDGE ENGLISH READERS, a level 0 book.
  On Friday 26 July: 6.30 am, Dr Janet Leighton was found as a body. She was killed by some one. Frank Williams was a police inspector and Kate Miller was a sergeant. They tried to solving this issue. Janet was a doctor. Barbara had been a doctor at Janet Leighton's clinic. But now she hated Janet because she fired by her. Simon was Janet Leighton's husband. He hated her because she didn't give him money or house despite she was rich. Chris Leighton was Janet Leighton's son. He was twenty-eight and hadn't any job. He also hated Janet because she didn't give him money.

Who killed Janet and why?
The killer is in those characters...