The internet world she inhabits is not much like the Los Angeles of Raymond Chandler’s hard-boiled hero Philip Marlowe.

Thousands of Britons are joining her world by signing up for the internet-based game Second Life. They invent their own character and plunge into an alternative existence which can make real life seem humdrum. Markie has flowing red hair, elbow-length gloves and femme fatale figure squeezed into a burgundy corset. As for her staple business: could anybody really care about sex between consenting clusters of electronic pixels?

They could and they do. Envy and infidelity are just as common and equally damaging to relationships on the internet as they are in real life and Mac’s Detective Agency is thriving as a result.

In many cases the bound- aries between the real world and Second Life become dangerously blurred because the relationships formed there are real and sometimes raw with emotion. Suspicious partners are now hiring her and her staff to spy on the internet activities of their loved ones.

Online gaming has existed for well over a decade but it is only in the past few years that “massively multiplayer online role-playing games” (MMORPGs) such as Second Life have taken off.

There are now an estimated 350 MMORPGs worldwide and their millions of subscribers have created a thriving independent economy worth more than £200 million in real cash. Most are geared towards empire-building through violence or commerce, which helps to explain why last December an Australian man paid £13,700 for an imaginary island, complete with ruined castle. Second Life differs from other games because it has no defined goal. The only limits to the ways characters can interact are the players’ imaginations and a Utopian code which prohibits actions that “marginalise, belittle, or defame individuals or groups”.

According to the technology website Wired News, Second Life is home to a community of real-life cerebral palsy sufferers and a clan of people with autism and Asperger’s syndrome who use the game to explore the social interactions that most people take for granted.

In another part of the game, American business school students are soon to begin road-testing their entrepreneurial ideas. Mac’s Detective Agency is just one among many businesses in this alternative world.

By day “she” is an IT manager of unknown gender somewhere in Scotland. By night she manages and pays an international staff of 12 private eyes who keep her Second Life offices open 24 hours a day. Markie has earned about £50 in real money in the past few months.

“It started as word of mouth,” she said. “We have people in love and getting married in SL and getting married is a commitment not to be unfaithful. I could see people who were married in SL paying for dances, sex, etc, and thought ‘I wonder if their partner knows’.”

The initial client interview can be harrowing. “I’ve had two people walk out. We try and warn people that some people may not be as serious as the other (person)”.

“Honey traps” are the agency’s preferred method: an attractive male or female character flirts with the target and then a sleuth photographs the couple in flagrante or, because this is a very different world, teleports the suspicious spouse right to the scene.

For the many couples in Second Life who are also together in the physical world, the consequences of an internet fling can be devastating.

Laura Skye and her “in-world” partner Dave Barmy also live together in real life.

When Laura found out that her boyfriend’s character was visiting a prostitute in the game, it reopened scars from her previous real-life marriage.

Feeling let down, she hired Markie Macdonald to tail Dave Barmy in the game and was delighted to learn that he had reformed his behaviour.

They married (in Second Life) last night in a lavish ceremony.

PLAYING IN ANOTHER WORLD

SECOND LIFE is an extraordinary alternative world where you can do anything you want (writes Ben Hoyle). It costs $9.95 (£5.25) to join the 25,000 subscribers, with a free trial for seven days. Your character is taught how to walk, pick up objects and fly. The highlight is the customisation stall where you turn your generic male or female “avatar” into something truly personal — right down to the bushiness of your eyebrows and the curve of your “love handles”.

Once inside the game, you interact with other players through Instant Messaging, a kind of continuous e-mail. You could engage in a philosophical discussion on the Iraq war (there have been charity fundraisers for the troops) and there is a virtual nightclub scene that caters for every musical taste and sexual peccadillo. I ended up in The Edge. As the green sun set, a blonde in a bunny girl costume, a woman in leather chaps and a hunk wearing a dogtag and red shorts were bumping and grinding to hip-hop. Lacking the skill to sit down, let alone dance, I felt surprisingly awkward and sloped off for a drink in the real world.

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