George and the twins are going blackberry picking. They'll be taking a large picnic with them made by George's mum. On the face of it, it sounds like it'll be a lot of fun. But George doesn't exactly appear thrilled when he asks Tom Oakley if William would like to tag along.
His disgruntled expression gives the game away; he's only asking because his mother has told him to. She's made a large picnic, large enough for William as well as George and the twins, and would clearly like William to sample some of the food she's made.
What's bugging George is that the twins will be angry when they find out that someone else will be coming with them. He's been placed in a difficult situation by his mother, and there's absolutely nothing he can do about it.
To make things just a little more complicated, Zach asks if he can come too. This is the last thing George wants. One strange town-dweller is enough, but two? That's beyond the pale. But under the circumstances, George can't very well refuse Zach's request, so he reluctantly agrees to let him tag along.
Sure enough, when the twins find out that two "townies" are accompanying them on their blackberry-picking and picnicking jaunt, they're far from happy. For one thing, they've heard that one of the evacuees talks too much—that would be Zach—and the other one talks too little. No prizes for guessing that this refers to William. Small wonder, then, that the twins think it was rotten of George to ask them to come along.