Dudley and Harry manage to get rid of Dudley's gang, but the afternoon devolves into "one thing after another".
Vernon gets moved from the cupboard under the stairs to being locked in the downstairs bathroom instead.
Draco Malfoy and his goons show up disguised as Death Eaters and gets his nose broken after being punched by Dudley.
Snape wakes up and sorts that out. But the dinner that is in the oven is ruined, and there are no more groceries to make a new one.
Vernon attacks Harry -- while Harry is holding a wand again -- and gets turned into a toad.
Petunia escapes and attacks Snape (more than once) and gets turned into the shrew she is so insistent on being.
Harry can't make a dinner out of nothing and throws the job to Dudley.
Dudley knows how to order pizza.
With all of the unauthorized magic going on. Snape is expecting the Aurors at any moment. He alerts the Order.
Instead, they get Dememtors. (Umbridge is on the job still.)
And fortunately the Aurors show up at roughly the same time, and even more fortunately, it's Shacklebolt and Tonks. They know the Demetors have no business being there, and promise to investigate.
Snape is still fairly exhausted and considers himself to not be up to the challenges of dealing with Potter and the Dursleys.
Vernon and Petunia are disenchanted and Obliviated. Dudley promises to say nothing of what happened. Harry is moved to #12 Grimauld Place to rest and recover from the poisoning. Dudley asks Harry to write to him once he's back at Hogwarts.
After school starts up again, Harry writes with some information which he suspects relates too Snape. I'm not going to post the image, since it's someone else's work and I just adapted it. (This is a personal reading copy, so I feel no shame) But if you want to get the idea, Google "fossegrim" and check the images. I suspect you'll have no trouble figuring out which one I used.