It's not known what Kaiden was imprisoned for, but due to his knowledge of making the drug known as Feckmon, it was likely related to this.
Upon arrival on Earth following the mass escape from SAR TOP, Kaiden and several other Enixians began to establish their Feckmon drug trade on Earth, telling Zin - a Vardian scientist who had engineered the escape - that it would only be served to those from the Migar System. However, Kaiden and the Enixians did begin to give the drug to humans as well, with Jess' friend Mandy been one person who began taking it - the drug itself been dispensed in red pens that had been adapted to act like droppers. Due to their ultrasensitive senses and their eyes being a giveaway of their non-terrestrial origin, Kaiden and the other Enxians are shown wearing sunglasses all day, including at night.
Feckmon, the drug Kaiden and his people produce, however, has a negative impact on humans when taken a few times. Although intially providing a 'high', it makes humans very sick after using it several times - to the point of blocking up a person's heart due to human blood been different from the blood of the various Migar species. This occurred with Mandy, causing her to have to be rushed to the hospital after suffering a heart attack. Upon finding out about Mandy been taken to the hospital as a result of taking Feckmon, Zin angrily called Kaiden about serving humans the drug, before ordering him to stop serving the humans as he was 'jeopardizing their operation'.
When Jess talked to Mel about what had happened to Mandy, Cole overheard their conversation and visited the area where the nightclub had been - finding a red pen with some of the drug left in it, which confirmed Cole's suspicions of it been Feckmon and allowing him to realise Kaiden was responsible. In order to find Kaiden, Cole decided to track down the Feckmon manufacturing factory - measuring the traces of the powder that Feckmon starts as before it's made into a liquid. Managing to find the factory, Cole battles some of the group before learning where Kaiden is going to be next - using a modified Torch to exploit the Enixian's sensitivities before capturing their life forces.
Jess goes to the police station to give a detailed description of Kaiden, following what happened to Mandy. However, an alien at the Police Station alerts Zin as to what Jess is doing. Zin in turn calls Kaiden and explains that Jess is giving the police a detailed description of him - with Kaiden assuring Zin one of his men (Vax) will deal with Jess. After leaving the police station, Mel and Jess are attacked by Vax but escape after Mel uses her personal alarm - causing excrutiating pain to the Enixian due to his hypersensitive hearing - and allowing the women to escape.
Mel and Cole later meet up outside the club's location and work together, allowing Cole to gain access to the club by disguising himself as the Enixian bouncer. Inside, Cole tries to get Kaiden to come outside by claiming Zin is waiting for him. However, Kaiden is distracted and Cole's disguise wears off - with Kaiden immediately recognising him as Daggon. Drawing his collector, Cole warns that he will take the life forces of many and that it will be painful. Kaiden - relaising the danger he is in - attempts to flee, but Cole catches him using his hypertime ability, with Kaiden screaming in pain as his life force is extracted. Cole then narrowly flees with Mel (with him clinging onto the top of her car as she drives away) as Vax and several of the inmates at the bar pursue them but are unable to catch them.
Mandy later recovers from her heart attack although Jess is told it will be a few months before she will be 'back to normal'. Meanwhile, Cole goes out on a date with a woman called Tiffany - whom he met and helped out the day before during his search for the Feckmon factory.
Tracker (TV Series) - Episode 2: Cloud Nine