Last Day in Limbo by Peter O'Donnell

When Modesty Blaise and her loyal lieutenant Willie Garvin try to take revenge on a man who mistreated their close friend, Maude Tiller, they never imagined what events would unfold. They discover that another companion, Danny, has not been dead for two years, as they had thought, but instead has been taken to Limbo, a plantation in the jungles of Guatemala. There slaves are tormented by the despotic Mistress of Limbo, aided by her ferocious armed guards.

Modesty allows herself to be captured in order to infiltrate Limbo, but places herself in great danger. For the plantation is to be shut down, and the slaves destroyed. Modesty must incite revolt to save both herself, and the captives, and hope that Willie brings help in time...