The authors propose a theoretical sequence for the psychological development of couples from narcissistic, autistic-contiguous and paranoid-schizoid levels to depressive position functioning. The authors illustrate their observations with vignettes from couple therapy with a husband and wife who are dealing with the impact of a third on their fragile relationship, initially in the form of their baby, subsequently his lover and lastly the couple therapist. They show how dealing with resistance and transference enables the couple to give up a shared manic defence, grieve together and move along the developmental levels to achieve a more satisfying reality.