"Something is going on. There's activity." Lloyd Lynch, a Trinidadian seismic expert, was listening through earphones to a solar-powered seismograph planted beneath the western rim of the Soufriere Hills volcano.
The seismograph was emitting an uneven drone. "If it starts going 'weeooo'," said Mr Lynch, making like a police-car siren, "that's when we're out of here. But by that time, you'd be seeing something."
We already were. "Is that steam?" asked Royal Marine Lieutenant Connor O'Hara, who had led us up the slippery, narrow edge of a 1,000-ft ravine to the western wall of a peak known as Gage's Upper Soufriere. Thick brown smoke was rising from the crater beyond the peak.
"Yes, but it's been doing that regularly," said Mr Lynch, an electronics engineer at Trinidad's University of the West Indies. It was not enough to make him leave before swapping batteries on the seismograph, a key instrument in assessing whether the volcano might blow.
Grinning, he then began doing a calypso routine on the grey mud deposited by earlier rumblings. "My scientist colleagues will pick this up back at Vue Pointe [their base]. It'll get them going," he said.
From just beyond the peak, on the crater's very rim, two marines opened radio contact. "Base, this is target. Over. We're halfway there." The commander of the 70-man marine force here, Falklands veteran Captain Paul Mansell, and Sergeant Kev Foster of the elite Mountain and Arctic Warfare Cadre, had hiked to the 3,000-ft Chance's Peak to place a reflector where scientists could see it.
On a rocky outcrop by an ash-shrouded mango tree a few hundred feet below the seismograph, John Shepherd, a vulcanologist from Lancaster University, had set up his tripod. But the mist meant we could still not see the two marines.
"If we don't get eyes-on, they'll fire a flare," said Lt O'Hara. To Capt Mansell, the hike across the crater rim of a rumbling volcano may have seemed small beer compared to the Falklands. He took part in "The Great Yomp" from San Carlos Water to Mount Kent and saw combat in the battle of Two Sisters Hill.
"When the reflector's up, I'll fire laser beams that will tell me, by distance and angle, whether or not the crater is bulging," said Dr Shepherd. "But I can tell just by looking at the outer wall from here that it's not. So far.
"There's a one-in-three chance of a little rumble while we're up here. But it's unlikely to be major," said Dr Shepherd. "You're standing looking up the gun barrel. But if I thought it were about to happen, I wouldn't be standing here smoking a cigarette."
If the volcano staged a major eruption, red-hot rock, ash and steam would surge westwards through a gap in the rim caused by an eruption 16,000 years ago. That could engulf the capital, Plymouth, which remains evacuated.
On our uphill trek, dead dogs lay on street corners. In a roadside field, three dogs tore at the flesh of a brown cow that had apparently died giving birth. In the otherwise deserted streets of Plymouth, we bumped into a young man in T-shirt and army-style trousers. "Marines?" I asked. "Bats," he replied. "I'm studying bats."
Matthew Morton, from Bristol, was trying to find a so-called Fishing Bat, a species with a three-foot wingspan that dives for fish, which he had previously radio-tagged with a miniature transmitter. "Bats are the only mammals native to this island." Was he a chiropterologist? "They usually just call us batworkers."