Richard 'Dickie' (Lionel Stander) and his dying partner in crime Albie (Jack MacGowran) become stranded after attempting to cross between Northumberland and Lindesfarne Castle which is inaccessible during high tide.
Dickie looks to the nearby castle for the use of a telephone in order to phone his mob boss and upon startling the resident owners, the neurotic George and his wife Teresa, Dickie holds the couple hostage as he waits for the mob boss to arrive.
Because Roman Polanski mostly focuses his film on these three he allows the trio to develop such a variety of characteristics that it seems very bizarre for them all to appear in the same film, never mind in such a limited number of protagonists.
Much of the problem with Cul-De-Sac is that the characteristics of the people are just so outlandishly unbelievable. How would the ambiguous George manage to tempt such an unsettled wife to live with him in a castle (which, by the way, is a fantastic set)? How could Dickie manage to instil such a fear into the occupants so they don't harm him in spite of numerous opportunities?
In truth, the film's singular redeeming feature is in the ending which is as dark and bizarre as the rest of the film.