The first, René, a mathematician, arrives at Cambridge to complete a PhD but is desperate to keep his real intentions for study a secret.
The second, Ruth, René’s supervisor, eager to rise through the ranks of the university.
The third, Diego, Ruth’s husband, and a philosophy lecturer trying to save his department from budget cuts.
All is well, until René begins an affair with Ruth and then with Diego. The modern ménage à trois explodes gender, love and sex and, using the lens of geometry, reveals equal relationships are indivisible by three.