An American Historian on Oxford's High Street

A tenured history professor at a midwest university has settled into his life after the death of his wife in a car accident. He uses the summer for academic research or to have a pleasant break teaching a course in Europe or in the US. He is still in his forties, but the love of his life is gone and a daughter is in Manhattan and a son in Minneapolis. 
For the summer, he will teach a course at Oxford University in England. There, on the High Street, a former student sees him. For the balance of the summer, they enjoy each other's company, but no more. Things change, though, during the next semester, he outside Chicago, she in Cambridge, Mass. This is a story of their romance.