Sentence:  Marcher said to himself that he ought to have rendered her some service - saved her from a capsized boat in the bay, or at least recovered her dressing bag, filched from her cab, in the streets of Naples, by a <WSD>lazzarone</WSD> with a stiletto. 
Meaning of the word marked with <WSD> tags:  One of the poorer classes of Neapolitans; beggars.