Mission to Venice — Raymond Marshall

Don Micklem, a millionaire American playboy, tells his secretary that he is looking forward to “four lazy weeks in Venice.” He has just finished to hectic months of work and plans to take time off, but he'll soon find out that sudden death lurks along the canals of Venice, and his visit to Venice will be far from a vacation, as he ends up fighting a ruthless political organization and narrowly escaping his own violent death.
In “Mission to Venice,” a thriller set against the background of Venice's sinister waterways, Don follows the trail of a disappearing one-time British agent: Has he been murdered or has he committed treason?