Cat heck

The Senior Upstairs Tenant has flown back to New England to care for an ailing family member, so the Child is staying with me 7×24 for the next two weeks. We put down the little futon next to my bed, right in the middle of the main free floorspace in my bedroom. Yesterday one of the cats peed on the futon. Today I caught Port, the female, pooping on it. These cats have never had a problem like this — I assume this is her telling me to get the futon out of her floorspace. I am severely ticked and trying to figure how to deal with this. Suggestions welcome.