Eric Ambler 
Siege at the Villa Lipp [PDF ebook] 
Send No More Roses

Professor Krom believes Paul Firman, alias Oberholzer, is one of those criminals who keep a low profile and are just too clever to get caught. Firman, rich and somewhat shady, agrees to be interviewed in his villa on the French Riviera. But events take an unexpected turn and perhaps there is even someone else artfully hiding in the deep background?