We hear about O. Brown quite a bit before we meet him. He is the Mr. Brown a neighbor talks about when he's gossiping about the shenanigans on the village Fete Committee. And Tarquin O'Connor mentions him, saying he's a recluse and a bit of scholar, just like Andrew, which makes Andrew recall that his grandfather had always said "Mr. Brown is not for us, Andrew, but we have to be very polite to him."
Tarquin adds that it's odd that Mr. Brown has lived there for so long, but nobody seems to know him. Andrew wonders about that too, but it's not until he meets Mr. Brown's Security a short while later and is told to get off Mr. Brown's land or he'll set his vicious dog on him, that Andrew really begins to feel furious. He knows for a fact that he owns all the land in that wood, but Security denies that, and tells him the wood and the house belong to Mr. Brown.
Andrew strides off in a rage, and when he gets home, pulls out the maps and his deed and verifies that the land belongs to him. Still in the same rage, he rushes out and gets in his car to drive to Melstone Manor, where this Mr. Brown lives.
There he meets Mr. Brown's butler and is grudgingly taken in to meet Mr. Brown, who is a tall, silvery gentleman in a smooth pin-striped suit. He immediately insults Andrew by saying he is glad to meet the tenant of Melstone House, and since Andrew is the owner of that house, he is not happy at all.
And Mr. Brown then proceeds to tell Andrew that he has been deficient in his protection of Melstone Manor, that he has allowed counterparts to stay in the vicinity, which is threatening to Mr. Brown, and that it looks as if Andrew is trying to consolidate a power base. He even explains what he means by counterparts, which is that they are people who resemble, in looks and in powers, the people who work for Mr. Brown, and adds that if Andrew would just take the trouble to read his field-of-care agreement, he would do much better.
He also says that he is at the Manor at the moment to avoid his former wives, who have some sort of lever they are using against him, and expects to be there until he can eliminate that lever. He then rudely tells Andrew it's time he was going.
Andrew rushes off, still furious, and doesn't calm down until he has gotten home and played his piano a bit. When Aidan comes back from playing football with the village boys & girls, he is almost himself again. But it's very clear that O. Brown is nothing but bad news.