In the novel The Clocks, Gretel is the housemaid of Mr and Mrs McNaughton of No. 63 Wilbraham Crescent. She is from Denmark, and appears to have no sense of time.
Colin Lamb, pursuing a counter-espionage investigation linked to the Larkin case told Inspector Hardcastle that he was on the lookout for any "foreign help" among the households. When they met Gretel, Hardcastle noted that here was the "foreign help" at last.