Thicker than Water is a 1993 Welsh thriller television film directed by Marc Evans and starring Theresa Russell, Jonathan Pryce, Robert Pugh and Catherine Neilson. It is based on the novel of the same name by Dylan Jones, about a Welsh doctor who attempts to put his life together after the death of his pregnant wife.

Plot

Debbie and Jo (both portrayed by Theresa Russell) are identical twins. Jo is killed in a car accident, and her husband, Cardiff physician Sam Crawford (Jonathan Pryce) is grieving for her. Despite this, Debbie starts to act increasingly like Jo for Sam to overcome his grief. Sam meets with, and is drawn to, Chloe (Catherine Neilson), his wife's former colleague. Meanwhile, Debbie, whose fertility problems seems exacerbated by a post-viral weakness, insists that she still feels Jo's presence. Mysterious circumstances lead Sam to suspect that Jo's death wasn't an accident at all.