Slippery Staircase

When one elderly spinster slips at the top of a long staircase and dies, it's business as usual for Chief-Inspector Macdonald. But when her sister dies the same way the Chief-Inspector starts to get suspicious. This 1938 potboiler will keep you confused to the bitter end but the imperturbable E.C.R. Lorac wraps it all up neatly.