They should call it a Don't Panic Room - an impregnable burglar-proof chamber that is fast becoming the must-have accessory in every well-to-do American household.
But what happens if the very thing the intruders want is in there with you?
That's the case in David Fincher's slick new thriller, a perfectly constructed recipe for buttock-clenching, palm-sweating tension.
Newly divorced Meg Altman (Foster) is spending her first night in a spacious New York house with her young daughter Sarah (Stewart), unaware that three ruthless criminals are intent on robbing the previous occupier's secret safe.
With seconds to spare, the two women - one claustrophobic, the other diabetic - enclose themselves in the panic room, setting in motion a brutal game of cat and mouse and a dangerous race against time.
A journeyman director might feel limited by a film where all the action takes place in a single house, but Fincher takes up the challenge with dazzling visual flair.
His camera prowls up stairs, glides through walls, and, in one amazing computer-assisted tracking shot, follows the villains from inside the building as they inspect the exterior for weak points.
Foster - who took over the role after Nicole Kidman pulled out, despite being four months pregnant - is endlessly resourceful as the imprisoned heroine, while Forest Whitaker is convincingly conflicted as the most sympathetic of the bad guys.
Only the film's eagerness to cut to the chase - there's little time to get to know the characters before they are plunged into peril - mars an otherwise hugely accomplished slice of Hitchcockian suspense.