When Licinius Murena, wealthy owner of a fish-farm, is found dead, drowned in one of his own eel tanks, not many tears are shed. Certainly not by Trebbio, who had just been booted out of his cottage by the landowner, and was heard bad-mouthing him drunkenly in public the day before Murena's death. Nor by the widow, a little stunner half Murena's age who allegedly spent an inordinate amount of time 'under the doctor'. Nor by his daughter or his farm manager. With friends like these, who needs enemies? Marcus Corvinus is the man to find out. With the help, of course, of his clever wife Perilla - if she can spare the time from her newly acquired passion for gambling...As we follow the Byzantine thought processes by which our hero solves the crime, we are entertained along with way with accounts of pisciculture and with a handy guide to 'Twelve Lines', the Roman precursor of backgammon.