The way Marc Mulholland tells it, there wasn’t anyone whom Emmanuel Barthélemy didn’t itch to kill. During his London exile the young Frenchman had Karl Marx in his sights and later made plans to return to his homeland and take out the newly installed Emperor Napoléon III. As a teenager in 1839, Barthélemy tried and failed to murder a Parisian policeman and 13 years later he succeeded in finishing off a rival political exile in a duel on the Surrey hills (the last fatal duel in England). The next killing came in 1854 when Barthelémy bashed and then shot George Moore, a harmless soda water maker and writer of light verse who lived in London’s Warren Street and mostly minded his own business. Let’s not forget the neighbouring greengrocer Barthélemy slaughtered as he fled the murder scene. That was the one he ended up swinging for.

This makes Barthélemy sound like a deranged serial killer whereas, according to Mulholland, he was actually a courageous revolutionary with a shocking temper. Born too late for the heroic convulsion of the French Revolution, Barthélemy was obliged to do his best in the silver age of discontent, that period from 1830 to 1860, during which someone, somewhere could be guaranteed to be plotting to overthrow something. In 1839 he was jailed for his part in a republican uprising, while in 1848 he manned a barricade during the episode of street violence known as the June Days. It was this incident that Victor Hugo seized on in book five of Les Misérables (1862), in the process turning Barthélemy into the very pattern of a proletarian leader. Indifferent to personal or factional advantage, Hugo’s Barthélemy is selfless, brave and powered solely by the anguish of his people.

Hugo succeeded in making him a hero, and now Mulholland is left with the unenviable task of making him real. Unenviable because Barthélemy’s life, more than most, lacked shape and sense: it was full of false starts, lay-bys and fizzlings out. Plus there’s all that murdering, which makes him hard to like. Which is why, presumably, the Oxford historian has chosen to situate this, his first foray into popular history, in that most fail-safe of genres, true crime. Indeed, the first few pages contain all the tropes of a Victorian murder mystery of the types that have become so familiar in recent years. As Barthélemy and his companion, a mysterious veiled woman, make their way through the murky streets of London there is a crowd of milling workers, some shabby market stalls and a sinister pawnshop.

On arrival at 73 Warren Street they are met by a maid with a tallow candle and shown into a back parlour stuffed with hideous new furniture – cue the obligatory reference to podsnappery. First Barthélemy whacks the homeowner Moore over the head with a mallet and then finishes him off with a gunshot before scrambling for the safety of the streets, which is where he is eventually arrested.

By rights the narrative should at this point spool back to explain how the young Frenchman and elderly Englishman came to face off in Fitzrovia. Deprived of a whodunnit, we might reasonably expect a whydunnit. But that’s not on offer, either. According to various theories breathlessly touted by the newspapers at the time, Barthélemy might have killed Moore because the old man had gone back on his word to supply funds for the assassination of Napoléon III. Or, given that Barthélemy had recently done some work in Moore’s factory, perhaps he was simply after his wages. Or could the fracas be the result of some sexual scandal in which Moore was either being accused of being the veiled woman’s father or, alternatively, of failing to pass on money from a Catholic priest who had fathered the woman?

Frankly, it’s hard to care. For instead of a concise solution to the London mystery, Mulholland offers us a sprawling and familiar summary of French radical politics during the stormy second third of the 19th century. As the House of Bonaparte cedes to the House of Bourbon, which in turn gives way to the House of Orléans, which is then trumped by the return of the Bonapartes, the radical cafes of Paris are full of similarly precarious and porous factions. There are socialists, anarchists, syndicalists, revolutionaries, communists and Marxists – and somewhere in the mix is Barthélemy, slipping in and out of the story as much as the fragmentary and often hyperbolic sources will allow.

If Mulholland trusted his readers enough to be interested in these spotty sources, their biases and misdirections, their fibs and gaps, then he might have been able to make us see why Barthélemy became such a lightning rod for the political anxieties of the mid 19th century. But instead he attempts to smooth out the bumps in his subject’s biography, all the while trying to convince us that the Frenchman was “a magnetic personality”. But, honestly, he wasn’t, and trying to turn his bitty life story into a gothic murder mystery, with the promise of a very particular kind of narrative pleasure, smacks of bad faith.

• Murderer of Warren Street by Marc Mulholland (Hutchinson, £16.99). To order a copy for £14.44, go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £10, online orders only. Phone orders min. p&p of £1.99.