The action of book "Shot on Large Marine" is opened out in two cities - Saint Petersburg and Moscow. March, 1883. Лыков and Благово moved in the capital and serve now in Department of police. The ex-minister of internal affairs of Maquis shot oneself in the apartment. Complicit in embezzlement of public funds, he expected an arrest and investigation| apparently, did not survive nerves. But Благово suspects that murder happened. And criminals staged suicide, that deputize tracks. It turns out that death of ex-minister was advantageous to many. Благово goes to Nice to the widow of late sovereign, princess Юрьевской. Лыков meantime sets forth to Moscow on tracks two scoundrels - retired cuirassier and his handy man from criminal. With a risk for life a detective checks up all most frightful dens of criminal Moscow.