posted 9 years ago
There's a rotten egg in there. Remove the hen to a box or other closed container, inspect the eggs and if any are cracked or discolored, remove them. Sometimes eggs die, even an entire clutch can die, and the hen may not necessarily realize this. A healthy egg will look like a normal egg, a rotten egg is sometimes greasy looking, or may have tiny mites crawling on it.
If the bedding material is dirty, wrap the remaining eggs in a cloth to keep them warm and change the bedding quickly, then replace the eggs and the hen. If she's as angry as you say, she will probably sit right back down on them.