The White Sister by F. Marion Crawford

Five years after Giovanni Severi had left Rome to join the ill-fated expedition in Africa, his brother Ugo obtained his captaincy and at the same time was placed in charge of the powder magazine at Monteverde, which Sister Giovanna could see in the distance from her latticed window. The post was of considerable importance, but was not coveted because it required the officer who held it to live at a considerable distance from the city, with no means of getting into town which he could not provide for himself; for there is no tramway leading down the right bank of the Tiber. The magazine was actually guarded by a small detachment of artillery under two subalterns who took the night duty by turns, and both officers and men were relieved at regular intervals by others; but the captain in command held his post permanently and lived in a little house by himself, a stone's throw from the gate of the large walled enclosure in which the low buildings stood.

For some time it had been intended to build a small residence for the officer in charge, but this had not been begun at the date from which I now take up my story.