T cells seek and destroy cells containing viruses. They identify infected cells by the recognition of specialised proteins such as MHC class I molecules that display virus-derived proteins on the cell surface. But viruses like cytomegalovirus (CMV) disrupt the production of MHC class I molecules, thereby evading the T cell-mediated immune response. In March Nature Immunology, Veronika Groh and colleagues from the Fred Hutchinson Cancer Research Center, Seattle, propose a new mechanism by which CD8+ T cells detect CMV-infected cells even when few MHC class I molecules are present.