The information plaque (below) gives a brief history of the chapel and its earlier life as the Chapel for the Daughters of the Christian Union.
I think there is a mistake in the english translation as the french text appears to say the original role of Chapel was to convert widows and daughters of Protestants while the English version says it was for those who had been converted. I presume once the Protestant father/husband had died then the pressure was applied on his wife and daughters for a return to Catholicism. What happened to the sons, I wonder? The period in France known as the time of the Religious Wars were certainly interesting and often bloody.
The plaque also informs us that the sect disbanded in 1790, the time of the French Revolution and the establishment of the First Republic.
Unfortunately the Chapel was closed when we visited and I’ve found no references of significance on the web, so information here is rather limited. In true secular French style, the assistants at Tours’ Information Bureau thought the Chapel was the city’s synagogue! Perhaps readers of this blog may have more background details? Either way, do seek out this interesting side-street next time you’re in Tours.