House infestation of flies
Our son bought us a lily plant which still has not opened when we went on holiday a week later. Two days later the house was full of flies and after checking for the usual reasons, my son put the plant outside and got rid of over 200 dead flies. It must have been the plant. What caused this please?
The plant may have had some eggs in the soil or on the plant itself.
Treat the plant and soil with Neem OIl.
This should take care of the issue.