[1][2][3] The Clock family (tiny human-like "Borrowers") live under the floorboards at the Driver–Millman house, suspected but so far uncaught by the Matriarch, Mrs Driver (Victoria Wood).
Daughter Arrietty Clock (Aisling Loftus) is seen by her grandson, James Millman (Charlie Hiscock) and they become friends, but his grandmother's suspicions are heightened.
Mrs Driver berates James' father Robert (Shaun Dooley) for being away too much (though he is absent in order to seek work), but is concealing from him mounting arrears that may lose them their home.
Anxious to rescue her parents, Arriety argues with and leaves Spiller, but he follows and saves her from a street cleaning vehicle, and they seek safety by hiding in a miniature nativity scene at a church.
James distracts Mildeye and Jenny by telling them of more little people communities, and secretly puts a modified remote control car inside a vent duct to aid the Borrowers' escape.
Mildeye gets back to the lab just too late to prevent the Clocks getting away, and chases them through corridors, lifts and stairways, but they reach James who runs from the reception area with his friends inside his rucksack.
In the post credits, Mrs Driver slips a strawberry cream chocolate down the borrower hole and whispers "Merry Christmas".