Born in Hong Kong in 2007, Tracer survives and thrives in the repressive environment of his native country with his father, Tong Si Hung. Though the government places serious restrictions on body modifications, enforcement efforts are lax, so people come from far and wide to get themselves upgraded. He has more contacts in more different fields of endeavor than anyone on Earth (or, at least, in Hong Kong) and greater expertise with human augmentation than anyone else alive.
In 2027, Adam Jensen rescues Tong from a cell in an old noodle factory under Hengsha, where he is being held by Belltower soldiers. When Adam reaches him, Tong reveals that he knowingly allowed himself to be kidnapped by Belltower because he didn't want to "follow in his father's footprints". Tong knew that by getting into trouble with Belltower, his father would be forced to send him out of Hengsha and over to Hong Kong to escape the resulting danger. Later Adam unwittingly aids in his escape by setting off a bomb in a Belltower dockyard. While the guards hurry to the source of the explosion, Tong is seen slipping past as he hops onto a small boat. As Tong departs, he gives Adam a quick farewell before speeding off.
By 2052, Tracer Tong has rejected all ties to governments and corporations to follow his intellect and inspiration wherever they lead him. He is affiliated to and lives with the Luminous Path Society, one of the most ancient and powerful of Hong Kong's organized crime Triads. But Tong seems to be more neutral where the Triad Wars are concerned. Having no loyalties to manipulate, Tong is feared by Bob Page more than any other single individual alive, and thus Paul Denton is ordered by UNATCO to kill him.
Before Paul carries through with the assassination, however, Juan Ivanovich Lebedev convinces him that UNATCO is involved in a terrible conspiracy, and given the mounting evidence, Paul chooses to help Tong, Silhouette, and the NSF (which he becomes a member of). It is revealed that Tong has the technology to reproduce the Dragon's Tooth Sword and to deactivate UNATCO killswitches. Tong is also revealed as one of Alex Jacobson's contacts. When JC returns to UNATCO from LaGuardia Airport, he is ordered to assassinate Tong, but due to the events between then and his arrival in Hong Kong (which confirmed UNATCO's affiliation with Majestic 12), JC instead sides with the resistance, and his killswitch is activated.
To gain access to Tong in the Luminous Path compound, JC is instructed by the Triad's leader Gordon Quick to obtain evidence that Maggie Chow was responsible for the assassination of the Red Arrow Triad's former leader, and be the catalyst for peace between the Triads by informing Max Chen, the current Red Arrow leader, of Chow's treachery. When JC proves his loyalty, he is allowed to see Tong, who deactivates his killswitch and orders JC to fetch the ROM encoding for the Dragon's Tooth Sword from Versalife. This would allow both Triads to be supplied with the swords and would thus prevent a war over the sword. Upon accomplishing this, Tong orders JC to return to the VersaLife building to obtain the schematics for the Gray Death virus so that he can use them to devise a cure for the deadly disease.
After this mission is completed, Tong tells JC about the Illuminati, and tells him about the shipment of Gray Death to New York on a Chinese superfreighter previously owned by Illuminatus Stanton Dowd. Since Dowd knows how to scuttle the ship, Tong orders JC to locate Dowd in Hell's Kitchen.
Tong advises JC from that point (a sign that he fully trusts JC), especially when JC is in Paris. Around the time JC is taken to the home of Illuminati leader Morgan Everett, Tong suffers from an accident with the Gray Death sample he was working with, thus contracting the plague himself.
As JC leaves Vandenberg (the home base for X-51), Jock arrives with Tong, who seeks the help of X-51 leader Gary Savage, the only person other than Bob Page capable of providing him with a cure for the Gray Death.
When JC arrives in Area 51 for the final mission, Tong reveals that the cure was a success, and the virus is in remission. At the holocomm, Tong asks JC to destroy Area 51 and cripple the global network, to provide maximum freedom for the people, and prevent a single organization like MJ12 from gaining control of the world. JC follows Tong's orders (and a couple of other choices as well), thus triggering the Great Collapse.
In the year 2072, Tong still retains his steely manner from his days of dealing tech in the Hong Kong underground. He deeply regrets his actions after witnessing the devastation and violent anarchy that resulted from the Collapse. Still a political idealist, he is determined to reshape society through the free and open distribution of certain technologies, a "Great Advance." Remaining loyal to the Denton brothers, Tong became leader of the Trier facility of ApostleCorp, founded by Paul Denton. When Alex Denton arrives in Trier, he meets Tong at a local tavern, where Tong prods Alex to rescue "Her Holiness" at the Black Gate Ruins, and reveals the purpose of ApostleCorp, Paul's cryogenic stasis and abduction, JC's imperfect merge with Helios and subsequent suspended animation, and the technology of biomod infusions. He even gives Alex a perfected biomod infusion.
Tong later pleads with Alex to revive JC, who is in Antarctica, and protect him from Billie Adams, who wants to assassinate JC. He tells Alex about the portal to Antarctica at the Black Gate ruins, a portal only those with biomod infusions can use.
At Liberty Island, the final mission, Alex meets Tong again. Here, Tong assists with ApostleCorp's battle against the other factions. If Alex is affiliated with another faction, Tong will try to kill them.
- Like his father Tong Si Hung, Tracer Tong has natural dark marks on his face. Since he doesn't have them in 2027, they probably appeared between 2028 and 2052. In 2072 at the age of 65 years, his marks seems to have lightened considerably.
- When Adam "saves" Tong from Belltower prison, he berates him after learning the truth. Adam mentioning to him that his actions had put many lives at risk, telling him: "Sometimes, the more power you think you have, the more quickly it slips from your hands." Tong takes the quote to heart, and would remember it 25 years later.
- He supported Chad Dumier in the fight against MJ12 in France. By 2072, the two had become rivals.
- Tong suspected Maggie Chow of attempting to instigate a war between the Triads (he had a contact at the police station who investigated her). He told Jock to keep a close eye on her, and kill her if necessary.
- He is the only character who appears in the first three games of the Deus Ex series. He also assists each game's protagonist in their efforts.
- Despite the fact that Tong is not a member of the Illuminati, the computer in his lab is connected to Illuminati Information Systems.
- Tong's name is a big pointer to his involvement in questionable activities -- despite his aid with the protagonists. In the late 1800s and early 1900s with the beginning of the Chinese immigration, Chinese gangs were popping up called tongs (堂). Written 唐, however, it is a standard Cantonese surname that is the character used for the T'ang dynasty, and more generally to mean "China"..
- The name "Tracer Tong" is possibly a reference to a widely-used computer network diagnostics program called "traceroute" (often abbreviated "tracert"). The traceroute program is used to trace the route a network packet takes from one network to another, displaying the interconnections between network routers in a list.
- Tracer Tong's computer in Deus Ex: Human Revolution.
- "If you can make peace among the Triads, then perhaps I can help you with your difficulties."
- "See how easily our technologies turn on us? The more power you think you have, the more quickly it slips from your hands."
- "Every passing minute brings your friend Billie one step closer to murdering the only sincere leader humanity has ever had."
- "JC, the net's going... The net's going black! JC! No more infolinks, transmissions of any kind. We'll start again, live in villages... If you receive this, if you survive... Then find us. FIND US!"