Our hero is Umbi (an acronym for emissary of the bishop), sent by him to undertake an important investigation at Snæfell-glacier. In particular he is to look into the conduct and behavior of Jón Prímus, the old pastor at Snæfell. Fantastic rumors are rife: amongst other things it is said that a corpse is lodged in the glacier! Armed with his tape recorder and notebook, Umbi embarks upon his mission. He tries to question the weird locals, a weird lot, but gets evasive answers. Slowly he is dragged into a quagmire of strange happenings and his efforts to understand only make him confused. If at the beginning he is a chipper, a mere device, by the end of the story he is inextricably involved, a committed participant in the bizarre events.

Kristnihald undir jökli er fyrsta kvikmynd Guðnýjar Halldórsdóttur gerð eftir samnefndri skáldsögu Halldórs Laxness. Hún fjallar um "Umba", umboðsmann biskups, sem er sendur til að heimsækja séra Jón Prímus á Snæfellsnesi vegna kvartana sem borist hafa vegna hans.