“What’ll we do if the forecast is bad?” asked Ben.

“Run away,” said Lotti, licking gravy off her fingers. “Go by train.”

“What about Elsie?”

“Leave her with Frank,” grinned Lotti.

“Seriously, Lotti.”

“It’ll be fine,” she told him. “Look at the sky! It’s a perfect day for traveling. And here comes Frank looking really, really grumpy. That probably means he’s had good news.”

Lotti was right. Not only had the harbormaster confirmed an exceptionally calm forecast, he had also introduced Frank to the skipper of a Dutch barge, the Wilhelmina, which they could follow as far as Ramsgate.

“So everything is perfect,” said Lotti cheerfully.

“Blinking marvelous,” snarled Frank.

But even Frank’s mood lifted as they rejoined the Thames. It was late morning, the tide was still with them, sunlight was bouncing off silver wavelets. Round the Isle of Dogs they went, past the Royal Docks and out toward Tilbury. The dogs stayed below, but Lotti and Ben and Frank all remained on deck, each taking turns at the tiller while the others drank in the surroundings. The river grew wider, its banks flatter and further away, the sky ever vaster, until it was almost possible to imagine what it might be like at sea.

“It reminds me of home,” said Lotti when the city was quite gone and they were surrounded by marshes.

“Barton?” asked Ben, surprised.

“Not that home,” said Lotti, and under her breath she began to sing, the song about the nightingale that Moune had taught her in her garden when she was little, which she had remembered on the night she rescued Federico from being shot.

“Pretty,” said Frank. “What does it mean?”

“Oh, it’s a very old song, and quite sad, but beautiful too. It’s about a man who walks past a spring, and the water’s so lovely that he swims in it, and then a nightingale sings and he says, sing, nightingale, sing, since your heart is light. But the man’s heart isn’t light, because his lover turned him away after he refused to give her a rose.”

“Silly,” said Ben.

But Frank, remembering a girl long ago whose heart he had lost for just such a foolish reason, said, “Teach it to us.”

“What, in French?”

“Long journey ahead, Charlie. And French’ll be useful where we’re going.”