fat is in the fire, the

fat is in the fire, the

A course of action with inevitable bad consequences has begun; there's trouble ahead. For example, Now the fat's in the fire-the boss arrived early and will see we haven't even started work . This expression, with its allusion to fat dropping into a fire and causing a burst of flames, was already a proverb in John Heywood's 1546 collection.
See also: fat