It might seem a little strange that the head of a king was in the attic of a tax collector, instead of located on his buried body. The explanation is no less strange.
King Henry IV ruled France from 1589 to his death in 1610. Many attempts had been made on his life as king. One such attempt left him with a gash across his upper lip.
While in Paris in 1610, his carriage was stopped in the congested streets and he was assassinated. It was expected for him to be buried at the Basilica of St. Denis, north of Paris, where nearly every French king had been buried since 900 AD.
His body was embalmed and interred with the kings before him, and was left alone for almost two centuries. In 1793, during the French Revolution, a number of unusual decrees were issued (such as changing calendars and clocks).
One of these ordered the destruction of all royal tombs, including the one Henry IV was in. A mob tore through the crypt and pulled apart the royal corpses. They were carried outside and had quicklime poured over them to make them decompose faster.
As a result, most of the bones at St. Denis were lost. For a while, it was thought that no royal remains survived the French Revolution, but rumors continued to creep up. In 1919, the head of Henry IV was found and sold at an auction. Joseph-Emile Bourdais, the photographer who purchased it, could not convince any museums it was authentic.
When Joseph-Emile died, his widow then sold the head in 1955 to a tax collector named Jacques Bellanger. There the head remained until a journalist looked at it in 2010, and it was confirmed to be that of Henry IV.