In the spring of 2008 Ella Runciter, a partner of the firm for thirty-four years, entered half-life at the Beloved Brethren Moratorium in Zürich. Her husband has visited her once a month ever since, which is as often as the moratorium’s licence allows. Half-Life is his account of the first nine years of those visits.

It is not a memoir, or not only one. Mr. Runciter approaches half-life as he has approached everything else in sixty years of business: by measuring it. He records how long each consultation lasted, how clearly his wife spoke, what she remembered and what she did not, and how much of the half-life that remained to her each conversation seemed to use. From those notes, and from conversations with families and moratorium staff across Europe, he describes how a mind in storage declines: slowly, unevenly, and with surprising stretches of clarity late on.

The book’s most discussed chapters are about what comes in as the signal weakens: other voices from neighbouring cold-pacs, fragments of strangers’ memories, and on several occasions a young man who would not stop talking. Mr. Runciter treats these as a security problem, which in his view is what they are, and his recommendations for screening consultation rooms became the firm’s half-life privacy service.