We find the grave eventually. It looks nondescript - a stone slab with Chinese inscriptions, a joss urn in front of it and the usual hump of earth behind. What is odd about the grave is not the what of it, it is the where.
Brothers Charles and Raymond Goh are in a clearing in the Bukit Timah Nature Reserve, after walking a hiking path 1km from our start point, a carpark in Chestnut Avenue. Insects buzz around our heads. The roar of Bukit Timah Expressway can be heard, faintly. Out of sight of the path, hidden behind bushes, is this solitary grave.
Older brother Raymond rubs his fingers over the text, painted in red. It says this is the resting place of Chua Moh Choon, a powerful triad society leader who died in 1879.
"The colours are too bright," he says with excitement. It indicates that the paint was laid down recently. He points out another anachronism - the pattern of grinding marks on the slab show it was made with electric tools.
The first time the Chua grave was found was in the 1980s. Except the grave was in Upper Thomson Road. A decade after that, it vanished. No one knows who took it or why.
Then, recently, explorers from the Temasek Rural Exploring Enthusiasts group, while looking for another artefact, stumbled on this jungle grave, hidden from hiking paths. They tipped off the Gohs.
And here we are, at a grave that was lost and found, then lost and found again, assuming this new site has something to do with the disappearance of the old one. There are more riddles: Who made this modern replica of a 19th-century grave? For what purpose? And why here?
Most interestingly: Is this just a marker or did someone exhume Chua's remains and rebury it here, where they would be safe from urban development?
The brothers paint a spooky picture of a clandestine grave-digging, of men dragging slabs and equipment around the jungle, perhaps under the cover of night.
This venture has a bit of everything they love - decoding clues, making a connection to the past, the joy of discovery and, perhaps most importantly, the pleasure of telling the story behind the stones. The brothers are in high spirits.
"Solving a mystery, yes - and putting what we know to good use," Charles says.
Their exploits have earned them nicknames. "Tomb whisperers" and "tomb hunters" have been bandied about for their work in grave location and identification. "Ghostbusters" or "myth busters" have been used for their paranormal investigation work.
The Gohs see history everywhere. They cannot help it. On the hike back from the jungle gravesite, they point out mossy cement pillars. They formed a cattle fence, from early 20th-century structures that gave Dairy Farm Road its name. At the Bukit Timah Guild House, where we do the interview, Charles, 49, spots a rare item in the grass: a cable marker stone from the now-defunct Telecommunication Authority of Singapore.
The senior safety manager with a construction company says: "Every stone tells a story."
The media first took notice of the brothers in the mid-2000s, after they began pinpointing the graves of leaders and towkays whose names adorn Singapore roads and buildings, and for helping families locate the resting places of ancestors.
In 2012, in an overgrown patch across from St Joseph's Institution, they found the grave of businessman Chia Ann Siang, who had Ann Siang Hill and Ann Siang Road named after him.
Neither Charles nor Raymond, 52, a pharmacist, make a penny from their heritage work.
They work as a team. Charles researches historical maps and pores over old government records and archived news clippings. He is usually the first to walk an area, looking for signs of a grave.
Raymond is fluent in written Chinese and has an encyclopaedic knowledge of clan lineage. Finding a grave is not enough. You have to know when the burial took place, who is buried there and if that person left a mark on Singapore history. That is his job.
Take, for example, how the brothers found a forgotten graveyard near the Singapore General Hospital (SGH) in 2014.
Raymond's reading of temple records pointed to the existence of a cemetery in the Outram area. Charles found it drawn on colonial-era maps. Cross-referencing it to a current map, he noted an undeveloped area.
He walked the thickly overgrown patch, noticed the graves, then called Raymond to read the inscriptions. Their find was reported in The Straits Times and, this year, the Government's plans to redevelop the hospital complex include provisions to preserve the graves and heritage features such as the walls from an old asylum.
It all started in 2005, when Charles was a licensed freelance tourist guide, conducting "ghost tours" of Bukit Brown Chinese Cemetery, a site that was then known mainly to families who visited during the annual tomb-sweeping Qing Ming festival, joggers and horseback riders. It had been closed to burials since the early 1970s. His idea for holding tours there had sprung from how anything that gave him the chills also fascinated him.
Raymond participated in one tour and was hooked - not by how spooky it felt, but by how astonishingly old the tombs were.
"Some of them date back to the time of the Daoguang Emperor, who reigned from 1820 to 1850. I could not believe that tombs like that existed in Singapore," he says.
He was so intrigued, he started to do his own exploration and research of the site and also got a tourist guide licence so he could tell more people about it.
In search of a vanished past
A few years earlier, Charles had founded Asia Paranormal Investigators, a group dedicated to applying rational, scientific principles to spooky phenomena. The group is today largely a website and forum, he says. As redevelopment surges ahead in Singapore, causing old houses, kampungs and even venerated trees to disappear, calls have dwindled.
When the Government's plan to cut a highway through Bukit Brown surfaced in 2011, another chapter was added to the brothers' book of varied activities.
The pair, especially Raymond, began sharing their knowledge with the volunteer community, All Things Bukit Brown, that work to raise awareness of the cultural and historical value of the cemetery. The "brownies", as its members are known, conduct regular guided walks of the site.
Ms Catherine Lim, an editor of the All Things Bukit Brown blog, says Raymond has been doing "dogged walking" of the cemetery since 2006. "The site is big and you can walk and walk and you might miss something, so you walk again, then you see it. It's hard to see - the inscriptions are faded," she says.
Then, as both she and Raymond note, he has to keep a mental list of historical figures and names connected to people who have asked him to find long-lost ancestors. That list is cross-checked against each inscription.
Lim's blog carries heartwarming stories of descendants who had given up hope of finding a certain ancestor in Bukit Brown's thousands of graves, only to have them discovered through Raymond's sleuthing.
The president of the Singapore Heritage Society, Dr Chua Ai Lin, talks about how the Gohs "pick up things that everyone else has forgotten about Singapore history".
"They have been doing it a long time, in their spare time, at such an intense pace."
They are practical historians, combining research with fieldwork.
Dr Chua says: "Right in the centre of town, there is a jungle and there are ruins from the 1860s and 1870s. Under our noses, next to SGH. No one knew about it until they brought it to our attention."
That work led to real results when it was announced that redevelopment would preserve the historical finds, she says.
Raymond is the eldest of five children, comprising three boys and two girls. Charles is the third child. Their father, who died recently, was a taxi driver. Their mother is a retired hawker who ran a kway chap stall. Both sons remember long, foul-smelling hours spent cleaning pig intestines.
The Gohs grew up in a family that had one foot in the supernatural world. An aunt was a medium and both brothers have experienced weird happenings as children.
As a teen, Raymond trained to be a medium. In one initiation ceremony, a needle was inserted - bloodlessly - through both cheeks.
Charles, who says he has a more Western outlook than Raymond, was into horror and science fiction, and had what he thinks were out- of-body experiences when he was younger. Those experiences have taught them to keep an open mind.
In most cases that they have looked into as paranormal investigators, the supernatural can be ruled out. Charles says "99.9 per cent can be explained. It's only a tiny fraction that can't be explained".
Raymond is married to a part-time clinic assistant and has three children in their teens and 20s. His children have accompanied him on treks.
Charles is married without children. His wife is Christian and prefers not to be involved in his tomb activities, he says.
Even as Singapore's uncharted parts shrink, the brothers plan to go on searching for tombs or other marks of a vanished past. Charles says: "As we have this interest and the knack for it, we'll just keep doing it as a way of giving back to society."
Raymond says he will continue to help the brownies conduct tours when he is free. Otherwise, he will carry on trekking in Bukit Brown and its surrounding areas, which also contain graves. The site is larger than people think it is, he says.
"It is 162ha in size and has 200,000 tombs. There are still many unexplored areas," he says.
Join the team on a trek to look for a tomb thought to be lost. Go to str.sg/4cMg
Charles on Raymond: Good interpretive skills
Like Raymond, Charles says artefact-hunting is made a lot more bearable when you have someone there with you. The Goh brothers plan missions via e-mail and text messages. If they do not meet on missions, they meet a few times a year at family gatherings.
Charles will do much of the archive-related work, such as going through news clippings. While much of it is online now, he might still need to make a trip to the National Archives or the Singapore Land Authority for historical material.
He credits his older brother for being the one with the interpretive skills, in which the ability to decipher tomb inscriptions is married to a mental database of prominent Singapore families and where their estates used to be. Many landowners were buried on their land.
Many times, when they have to cut a path through the bush, Charles says he is glad for the company.
"Walking on a 8ha plot, bashing through thorny vines, it takes 10 minutes to walk a few steps. Many times, I find nothing," he says. So, being able to hear another person's voice nearby is comforting, he says. In the bush, they usually split up and shout to each other to stay in touch.
If he is alone, Charles says, he might take a screenshot of his location on Google Maps and text it to Raymond in case he needs to be rescued.
Raymond on Charles: Uncanny ability to navigate
Charles has a spatial intelligence that allows him to orient himself on a plot of land and see how maps drawn in different eras relate to one another, says Raymond.
"He's an explorer. If he has a map and compass, he can find his way. He makes it look simple," he says.
In the jungle where every tree looks the same, Charles' ability to navigate is uncanny. He is usually the first to enter an area, so he has to deal with the undergrowth. He can spot boundary markers only a few centimetres tall, fallen over or hidden under brush. "He can find a stone or a tomb in all that vegetation," his brother says.
Often, it is only after Charles has found something that he tells Raymond to come in for a look.
The heat, thorny plants and biting insects will make the less determined give up. Not Charles, who Raymond says will carry on hunting for days, sometimes weeks on end.
There is another thing that the two of them give to each other, without which their most important finds would not have happened - emotional support.
"People ask us, 'Why are you wasting your time in the jungle? You can go out and make more money for your family'", says Raymond.
"When I have someone along who is as foolish as me, it helps," he says with a laugh.