Fortunately, there are no Australians in our group.
"I need to warn you about dangerous plants," says Mike soon after we begin our three-day hike along the Hollyford Valley. He points to the leafy shrub beside him.
"This is tutu. It's poisoned circus elephants that ate the seeds. And that over there is stinging nettle."
He stops: that's it, the hazards of the New Zealand bush, done and dusted in less than 30 seconds.
Any Aussies would hoot scornfully at such an apparently wussy environment. But, as we've already discovered, even without lethal snakes and spiders there has still been plenty of danger and desperation along this river, which runs from Fiordland's mountains to the West Coast at Martin's Bay.
Shortly before getting to where the track begins at the end of the Hollyford road, we stopped at Gunn's Camp, a scattering of cabins around a shop and a little museum. Inside it are black and white photographs of doughty-looking men in battered hats.
Rusty iron tools, gold pans and horse-shoes are nailed to the walls, along with yellowing newspaper clippings recording landslides, floods and bridge wash-outs. Dominating the room, though, is a worn saddle on a rack, its label reading "Davie Gunns saddle he was drowned from".
Davey Gunn was one of the first farmers in New Zealand to diversify into tourism, leading groups on horseback along the river in the 1930s to boost his income.
But his most famous exploit is a ripping yarn that Mike tells with undisguised admiration, squeaking with incredulity when he describes how, in 1936, Gunn ran ("with a broken rib!") and rowed the 15km length of Lake McKerrow ("with mismatched oars!") to raise the alarm about a plane crash at Big Bay, covering 97km, a trip that normally took four days, in just 20 hours. This feat of endurance saved the lives of at least two men and earned him the Coronation Medal.
There are other Hollyford characters, too, like Maori chief Tutoko, who alarmed the first two Europeans in the area when they were confronted by him dressed in American Civil War military uniform.
And Frederick Fitt, stranded for a week on an island in a flooded river, without shirt, boots or socks, driven mad by sandflies.
And Margaret McKenzie, who gave birth alone on a bed surrounded by floodwaters.
And Robert Whitworth, who wrote in the Wakatipu Press in 1870 that at the mouth of the Hollyford Valley "there is flat, arable land as far as the eye can see".
On the second day, we stand there, in thick bush, the mountains crowding our shoulders, just along the river from the treacherous Hollyford Bar that claimed one ship in three trying to cross it, and marvel at the misery that the promise of gold brought to many unsuspecting settlers. Here, the only gold lies underfoot, an eternal autumn of fallen leaves from the lush forest of beech and podocarps, ferns and mosses.
The scenery takes our breath away, but happily in a figurative sense only. The Hollyford Track is a civilised walk, the highest pass just 168m, the hardest day the first 18km along the river. Clear, cold and turquoise, it's upstaged only by the mountains and glaciers gleaming white above our heads.
But Mike's keen for us to look more closely at the stuff in between, and his enthusiasm is catching.
We share his thrill in gazing at an unassuming fern, tmesipteris - "460 million years old! It's Jurassic!" - and nibble supplejack vine that tastes like asparagus, and furry brown tree fern tips that are meant to taste like walnuts but look and feel too much like caterpillars for any great enthusiasm on our part.
And then, at the end of a long day, we arrive at Pyke Lodge, with its dramatic view of Mt Madeline, for a warm welcome, a hot shower, elegant canapes and a classy venison and vegetable stack before a soft bed and a peaceful night.
Next morning, the mountains upside-down in a river-mirror, we detour for a look at Lake Alabaster before the cushy treat of a jetboat ride down the river to Lake McKerrow, leap-frogging the Demon Trail.
A walk through mossy forest brings us to a coastal track lined with bent-over trees and wind-whipped flax, and a rookery where instead of rooks there are seals and sometimes penguins.
After another night of comfort, at Martin's Bay Lodge, and a morning stroll along the sand, we're indulged with the ultimate luxury: an aeroplane at the door and a flight along the rugged coast into Milford Sound, dwarfed by the mountains above us. It's a suitably spectacular end to a truly World Heritage walk.
The Hollyford Track is a guided three-day nature experience with accommodation in comfortable lodges. The season runs from October to April. Transfers from Queenstown and Te Anau, jetboat and plane rides are included.
Pamela Wade was hosted on the Hollyford Track.