In the Migar System, Tevv was what humans would call a 'terrorist'. He injected himself with a very lethal Nodulian virus and proceeded to use it to kill several victims, including an important Cirronian Ambassador who (according to Cole/Daggon) did many great things. Just touching his victims was enough to kill them. He was later arrested and sent to SAR TOP - been the only prisoner with the virus.
When the Vardian known as Zin engineered the jailbreak that allowed over 200 prisoners to escape into Chicago on Earth, Tevv was one of the prisoners who escaped and took on a human body. In his human form, however, the virus has a negative trait in that it began to build up a poison inside his body - meaning Tevv had to get rid of it every day or it would kill him. Furthermore, the only way for him to get rid of it is through intimate contact with a woman. When the woman's body is sexually stimulated, the poison is drawn out and passes onto the woman - with the poison itself been lethal to humans within 3 to 5 Earth days. To avoid been caught, Tevv travelled around into other cities and visited the night clubs to look for women to pick up so he could get rid of the poison in his body.
When Cole and Mel investigate his actions after Cole sees a woman in the hospital with the virus (having driven Jess to the hospital after she hurt her arm), they enlist the help of the Desserian conman Nestov - who uses his enhanced sense of taste on a hand-towel that the pair recovered from the woman's apartment - to learn what Tevv is doing. After failing to stop another woman from getting infected, Mel decides to use herself as bait so Cole can take Tevv's life force and collect a blood sample from him to synthesize an antidote to the virus. Despite initially loosing track of Mel's position after she leaves with Tevv, Cole manages to find them at a Motel just in time and breaks into the right room - just as Tevv has thrown Mel onto the bed and tried to rape Mel when she refused to have sex with him. During a fight between Cole and Tevv - with Tevv proving to be a solid opponent - Mel is able to get a blood sample from him when he is distracted by stabbing him in the back with Cole's modified syringe (which he dropped in the fight). Although Tevv manages to knock Mel aside, she has provided the distraction Cole needed to restrain Tevv and capture his life force.
Cole would later create the antidote from Tevv's blood and give the antidote to all the infected women, with the women getting better after a few days. Talking at the Watchfire later, Mel wishes Jess a good night as she goes out with her boyfriend Gordon, but warns her to be careful. Talking to Cole later, Mel expresses her upset about not been able to capture Tevv earlier, Cole reminds her that it's his responsibility to capture the prisoners and take them home - adding that while it will take a while, he is getting used to been on Earth; with Mel adding she is getting used to having him around, before the two return to their rooms for the night.
Tracker (TV Series) - Episode 5: The Plague
Tracker (TV Series) - Episode 22: Remember When (Stock Footage)