I really can't believe that someone else snuck into the kitchen and added poison to the meal. If this "story" was set in an English village, a la Agatha Christie, in a row of cottages, it might be possible. But this house is in a semi-rural area. This imaginary poisoner would first need to get to the house - but how? Drive, and park outside the house? Park nearby? Ride a bike, and leave it nearby? Australia isn't full of little sunken lanes to hide cars and bikes in. Walk? But that takes longer, so a longer time to be spotted by somebody. And believe me, a pedestrian outside of the main town area would be very noticeable. Then what about the children? If the children were heading to the movies, presumably with a driver, this anonymous poisoner could easily have been seen. If the children were still at home, then there were 3 people to avoid, not easy. Also, he/she would have had to know about the lunch visitors, and that a proper meal was being cooked. And especially what was being cooked. You can't just rock up with a handful of mushrooms or some sort of poison in a bottle or a packet on the off-chance that you can slip it into the lunch. What if the lunch had been a simple cold collation consisting of sliced cold meat, a green salad, potato salad and pasta salad? Nope, I'm not buying it.