This chapter provides an introduction to psychodynamic theory as applied to settings outwith the specialist psychotherapy clinic, paving the way for the chapters that follow in Part 4. An individual’s internal world affects how they relate to others. Others may be unconsciously invited into playing old roles that are familiar to the individual (such as rejecting, not listening, criticising), even though these roles bring difficulty and distress to both sides. This chapter explores how these powerful but sometimes ‘invisible’ interpersonal dynamics may play out between service users and staff in settings where the human relationship is at the fore (such as schools, social service agencies, and hospitals). We also discuss splitting within a clinical team and other system dynamics. In circumstances where services and professionals can sustain a good-enough therapeutic environment in the face of unconscious invitations to repeat a problematic relationship, trust may develop between service user and service and many people are able to discover new ways of forming relationships. This depends partly on the capacities and current state of the person using a service, but also, crucially, on the capacity of the professionals and services to observe and be reflective about both sides of the relationship.