The friendship of Max, Sturdy and Gizmo has grown stronger in the trials that have befallen them since that strange and terrible day when all the people disappeared. The faithful Labrador, the determined taxi dog and the resilient Yorkie have gone through a lot together, supporting each other in a changed world, losing and gaining friends. Having escaped from the totalitarian nightmare created in the city by a Doberman nicknamed the Chairman, friends escape from his attack dogs on a boat. Now they have to uncover the secret of the three rings, which Max was told about by his old friend, the unusually wise black Labrador Madame Curie, who died due to the fault of the Chairman. And now the dark waters of the river carry friends to new adventures.