I'm with CliffordK. Got pics? There are at least a few different modes of failure and your repair options are going to vary accordingly.

Did the chain stay break? If so, why? Is there an underlying problem like corrosion inside the stays that could lead to additional failures? Or did the dropout separate from the stay, or maybe even break?

If the chain stay broke, it may be repairable via welding. If the dropout separated from the stay, it might be able to be brazed back into place. If the dropout broke, a new one can be brazed in.