But it was the black and white Flossie who had to find Polly and the horses because the tractor "got deeper and the wheels started to spin" after Jim drove his tractor into the river.
Henderson spoke with a friend in Owhango who took horse trekking for his latest book for kids, aged up to seven.
"I knew about horses but spoke with my friend to find out more about them."
Flossie and the river crossing is Henderson's ninth book.
The illustrations are by movie/animations director and lead animations Phill Simmonds of Simmonds Animations in Raumati.
Henderson writes under the pseudonym Cracker Jim and draws on his farming days in the Rangitikei.
Henderson left his organic farm at Whangaehu in 80s, spent a couple of years with his wife in London on their "grey-hair OE" before settling in Palmerston North.
And now the couple are embarking on a new adventure.
" I've always been doing wacky stuff," says Henderson.
The couple will soon be off travelling the country in a motorhome and selling Henderson's "Flossie" books.