Mrs. Harrison was a tourist on an island in the South Pacific.
In 1967 on the Tuesday just before Cate Archer arrives on the island, there was an incident with Mrs. Harrison, a Football and some Monkeys. Apparently the Monkeys became excited by the sight of the football on the beach. The resort on the island (secretly run by H.A.R.M.) had to issue a warning to guests that if they played football on the beach they did so at their own risk. This information was found by Archer in a letter to the guests.