A seemingly random group of six Londoners shows up for a retreat weekend at an almost-completed new luxury hotel. Each believes he or she is there for an intense group therapy session on how to pick up the pieces after a tragedy. As they begin to open up to one another, it slowly becomes clear that they are somehow linked together, that each person's tragedy is in fact the same - a young woman's suicide. Before they can decide exactly what this means, the phones and elevators at the hotel go out, effectively trapping them on the top floor until Monday. Then, bizarre "accidents" begin to befall them, one at a time.