An overdue book
Isabella was the archivist; Theo was the patron who had kept a nineteenth-century atlas out for three months. She sent a sternly worded letter. He replied with a sonnet.
Our story
The long courtship
Six years of letters between Providence and New York, one shared library card and a very patient cat called Orlando.
Midnight
Theo proposed at midnight on the winter solstice, under the observatory dome where they had first looked at Saturn together. Isabella said yes before he had finished the sonnet.