The red professor and the Russian princess

<jats:title>Abstract</jats:title> <jats:p>In 1916, Einstein stays in the Witte Rozenstraat for about two weeks, a visit that does him enormous good, as he writes afterwards, and that deepens the friendship between him and Ehrenfest. It also enhances Ehrenfest’s reputation in Leiden, where he guides Dirk Struik, Dirk Coster, Jan Burgers and Hendrik Kramers through their studies, and where not only his lectures but also his colloquia and lifestyle are a source of inspiration for others. Afanassjewa, meanwhile, tries to continue studying, working and writing from home.</jats:p>