Last Light — Andy McNab

The fourth in a series of Nick Stone thrillers, Last Light gets off to an exciting start as the ex-special agent has been assigned to carry out an officially-sanctioned assassination.
When Stone realizes who the target is, he refuses. But he is then given a chilling ultimatum: fly to Central America and finish the job, or the eleven-year-old orphan in his care will get killed.
Stone arrives in sweltering Panama, close to breaking point. His life is in pieces, but things only get worse when he finds himself caught at the centre of a lethal conspiracy involving Columbian guerrillas. Hundreds of innocent lives are at stake, and their only chance of rescue is Stone. But he has a critically injured friend to rescue, miles of dense rainforest to navigate and the toughest decision of his life to make…