Plotting
Just to make sure things are clear, this is what happened at ickle Ben's birthday party on Saturday:
When Andromeda arrives with Dora and Ax, Narcissa sees her, gets upset, and leaves with Draco. When Narcissa leaves, Walden notices Andromeda is there, takes Katharina to one side, and they have a spat. Andromeda notices Narcissa has left and Walden is mad at Katharina, and offers to leave. Katharina refuses the offer and spends the rest of the party cooing over Ax and Ben. Ax and Ben get on really well, and it's adorable. Lucius arrives at the party with Draco to vibe Andromeda out as they don't want him to miss out on the party. Lucius questions Walden about how Andromeda ended up there and why nobody thought to inform Narcissa. Walden spends the rest of the party glowering at Katharina. After the party, Walden and Katharina have a big fight (thread to follow), during which Walden strikes Katharina for the first time.