The Xanadu talisman - Peter O'Donnell

In this classic return we see
Modesty both at her most feminine and at her toughest. Trapped in an
earthquake disaster with a dying man, she makes a promise that is to lead her
and her faithful friend Willie Garvin into the most perilous crisis of their careers.
Their quest takes them from Tangier to Paris, from the Riviera to Corsica,
and finally to a stronghold in the heart of the Atlas Mountains, their every
move observed and manipulated by El Mico, the most notorious and dangerous
criminal genius in the Mediterranean. Unknown to Modesty, she holds a secret
that El Mico covets above all else, and she is brought to a final
confrontation with death in the stronghold of Xanadu. As in all the Modesty
Blaise stories, this book is peopled with a host of eccentric characters: the
engaging Dr. Giles Pennyfeather, Modesty's devoted friend, and her opponents
Little Krell, a prodigy in combat, the Silk brothers, juvenile adults who
deal in death, and the astonishing Nanny Prendergast.