Elena and Antonio discover that their parents have a very rare disease. Their only hope for survival is a stem cell donation that must occur in a very short time, and their children are the only suitable candidates for this particular procedure. Elena and Antonio prepare for the operation, but Antonio discovers that he's not a match for the donation, and Elena's stem cells are not enough for both of them: it's not possible to cure both parents. Whose survival will they choose? And who will they let die? A dramatic decision that will force brother and sister to come to terms with their entire past and bring to the surface their fiercest instincts.