Here we will discuss leaks found in and around a fireplace.
Water leaking into the fireplace
If you have a cap, the problem might be more serious. Cracks or holes in the crown (the very top) or in other areas could be allowing water to leak into the chimney. If so, masonry repairs are in order, for safety and to fix the water leak.
It is also possible that pooling water might be soaking through the structure and leaking in. A water repellent treatment will help if this is the case.
In any case, it is wise to consult a chimney professional, as water entering the chimney will gradually damage the chimney structure, and could indicate a serious problem.