<p>Clinicians have long used the phrase the hidden patient to describe the relative who cares for a declining elder and whose own health quietly fails in the process. The moral philosophy of ageing has not taken the phrase seriously. It has concentrated on the older person, on her autonomy and her dignity, and has left the family that sustains her at the margin of attention. This paper argues that the phrase is more than a clinical courtesy. When serious illness and frailty arrive in later life they characteristically produce a second patient, the carer, whose suffering is real, measurable, gendered and, for the most part, unrecognised. We defend the claim on two grounds that the existing literature has kept apart. First, we extend the phenomenology of illness from the patient to the carer, showing that the contraction of the lifeworld that phenomenologists describe in the ill person recurs, in a related form, in the person who tends her. Second, we identify a moral hazard internal to care itself, by which the responsiveness that makes family care valuable is also what exposes the carer to exploitation, so that her love is enlisted as a substitute for social provision. We trace the invisibility of this second patient to the model of the independent self that governs modern moral thought, and we draw out what follows for clinical practice and for justice. The carer is owed the standing of a co-patient, not the gratitude reserved for a volunteer.</p> Graphical abstract <p></p>