In the summer of 1934, "a sickly pathetic marmoset" called Mitz came into the care of Leonard Woolf. He nursed her back to health and from then on was rarely seen without her on his shoulder. A "ubiquitous" presence in Bloomsbury society. Mitz moved with the Woolfs between their London flat and their cottage in Sussex. She developed her own special relationships with the Woolfs' spaniels, Pinks and Sally, and with various members of the Woolfs' circle, such as T. S. Eliot and Vita Sackville-West.

She accompanied the Woolfs on their holidays, including their travels through Europe, and played an important role in helping them to escape a close call with Nazis in Germany.

Using letters, diaries, and memoirs, Nunez reconstructs Mitz's life against the background of Bloomsbury in its twilight years. Although a turbulent period marked by the threat of war, the deaths of beloved friends and relations, and Virginia's near breakdown under the strain of finishing her novel The Years, it was nevertheless a time of much happiness and productivity for the Woolfs.

Tender, affectionate, and humorous, Mitz provides a glimpse of what Virginia Woolf once described as "the private side of life - the play side," which she believed one's pets represented. Through Nunez's skillful storytelling, an intimate portrait of a most uncommon household emerges - a celebration of the love that saw one monkey, two dogs, and modern literature's most famous husband and wife through some of the worst of times.