Help, cats hate each other

[CatIshoo]

Our cat was like the prodigal son and came home, in March, after 8 months away. Before she went their was a mutual understanding to stay away from her, between her and our other cat, Arthur.

While she was gone we got a kitten who gets on great with Arthur (they are inseparable, they sleep cuddled up)

Since she has come back it's been hell. We have to keep her separated from the other two and if they come across each other there are massive fights.

We have tried the plug in stuff but it's getting worse, not better.

Has anyone got any ideas?

[patienceisvirtuous]

Could you start from scratch by separating them and doing the slowly slowly introductions/exchanging scents etc...