Night Watch (Alistair MacLean's UNACO) by Alastair MacNeill
Someone has stolen the world's most famous painting and replaced it with a fake. When the mission looks impossible, the world calls upon UNACO.
After lengthy negotiations the Rijksmuseum in Amsterdam agrees to send its priceless Rembrandt, `Night Watch', on a tour of the world's art galleries. Security is intensive. Even so, when the painting arrives in New York it is discovered to be a fake.
UNACO is immediately called into action. Agents Mike Graham, C.W. Whitlock and Sabrina Carver must find out who is responsible for the brilliant forgery and, most important, who now has the original in his private collection.
Speed and secrecy are vital. The hunt leads them to Rio de Janeiro at Carnival time, where their quarry is secure in his mountain fortress, high above the sea...