It's not known why this Enixian was imprisoned on SAR TOP for, as it's not revealed in the series.
On Earth, the Enixian works as a bouncer for two other Enixian fugitives, Kaiden and Vax - who have set up a trade of the drug known as Feckmon. In order to avoid getting caught dealing drugs by the police, the night club moves around night after night. When the tracker known as Cole/Daggon investigates with Mel and discovers the Feckmon trade, Mel begs Cole to find a way to shut down the trade - as it's been proven that Feckmon causes heart attacks after a few doses when used by humans, due to human blood been different to the blood of aliens from the Migar System. Agreeing to shut it down by catching Kaiden, Cole asks for Mel's help in gaining entry to the club after learning of its latest location - as he will need pictures of the bouncer to replicate his appearance and gain access to Kaiden.
Later that night, Mel pretends to be getting mugged and starts screaming - drawing the bouncer away from the door. As he goes around the corner, Mel surprises him by taking his photo. Due to the Enixian's highly acute senses (in particular his hypersensitive vision), the flash of the camera disorientates him before he is restrained from behind by Cole and pulled to one side.
As Mel checks out the photo, Cole (out of sight) pulls out the Enxian's life force. Returning to Mel, Cole takes the photo and replicates the image of the bouncer - allowing him to access the club. Although his attempt at getting Kaiden outside fails due to the disguise wearing off, Cole is still able to take his life force before he and Mel escape.
Tracker (TV Series) - Episode 2: Cloud Nine