Sedra Valix and Vedra Valix - Better known more simply as the 'Valix Sisters' - were a pair of Orsian assassins who escaped to Earth from SAR TOP Prison, thanks to the vardian known as Zin, before taking on human forms.
The Valix sisters were both arrested and sent to SAR TOP from their home-world of Orsus after they murdered dozens of people - with Cole stating that they were very efficient at their 'jobs'.
Upon their arrival to Earth, they took on human forms (like Raahm and Saahm, their bodies were very different from the other) before been sent by Zin to a retreat to lure the tracker Cole/Daggon to them. The plan was to ambush and defeat/kill Cole before heading to the Watchfire Bar (where Cole's tracking operation was based) and steal the life-forces that Cole had captured before returning them to Zin to find new host bodies for. To ensure their success, the pair had managed to find a way to stop Cole from sensing them as the hotel was built over lodestone - meaning there is too much geomagnetic activity for Cole to sense their presence accurately. Zedra referred to humanity as "the most disgusting and useless race she had ever encountered" while Sedra described Earth as being a "stinking little hunk of rock".
Sure enough, Cole arrived with Mel after a tip-off from Nestov - the pair pretending to be a married couple (Mr and Mrs Hauser) wanting to 'put romance' back into their relationship. The seminar the pair end up going to was a new experience for both Cole and Mel - especially since the pair were only pretending to be intimate. Later splitting up, Cole investigates a possible trail after seeing Dr. Janet (the woman leading the seminar) and her 'third husband' been very close. He doesn't find anything, and ends up having to try to bluff to Dr. Janet about what he's doing when she catches him in her room.
Cole's attempts to locate the sisters at a party that night fail, as Cole tells Mel during a dance with her that the sisters know he's there. Having learned about the lodestone that the hotel is built upon, Cole tries to get Mel to leave with him as he states that if he can't sense the sisters then Mel will be in danger - stating he will catch them later on his 'own terms'. However, Mel refuses - stating that she and Cole are a team and that they work together to stop the fugitives, no matter what. Returning to the party, Cole has to dance with the Dr. Janet while Mel ends up talking to a woman called Erica. Seeing a man flirting with her despite his wife been there, Erica leaves to see him, although Mel follows after seeing the woman has left her handbag. Breaking from his dance with Dr. Janet, Cole embraces Mel and kisses her before leaving the party - due to picking up on the sister's telepathic messages.
Erica is revealed to be one of the sisters (Vedra), as she attacks the man who was flirting with her before breaking his neck. Tracking the other sister, Sedra - in the form of a large man called Chuck, who was posing as Erica's husband - Cole attacks her and tries to take her life force; only to be shot by an energy weapon from behind as Vedra appears. Restraining Cole, they inject him with a drug that knocks him unconscious. Using their technology, they acquire Cole's energy signature in liquid form.
Having found the woman's room, Mel enters before finding alien technology in their suitcase and pictures of the Watchfire - realizing Erica and her husband were the Valix sisters. Trying to find Cole, Mel overhears one of their conversations when she returns to their room and goes to find him. Seeing Vedra and Sedra leaving a closed off part of the hotel, Mel manages to gain access by punching the door window - cutting her hand in the process. Finding Cole, she tries to revive him - initially crying after thinking she is too late to save him. However, she manages to hear him weakly whisper the word 'power' and attaches electrical cables to his restraints, which re-energize him.
Leaving the hotel, Cole realizes Zin had laid a trap to try and have him killed, with the sisters planning to use Cole's energy signature to free the prisoners he had captured so far. As his strength returns, Cole thanks Mel for helping him when he first came to Earth - saying no one could have made a better partner than she has. When the pair get stuck in a traffic jam, Cole decides to go on his own as his strength has returned. Using his powers to heal Mel's hand, he then enters hyper-time and returns to the Watchfire. At the Watchfire, Sedra and Vedra (who keep continuously arguing like a married couple) find Cole's 'war room' and - after both expressing their negative opinions about how he was able to successfully capture so many fugitives with such a 'primitive' setup - find his prisoner storage unit.
Cole arrives and briefly fights Sedra, managing to avoid her attacks with the energy gun from earlier as Sedra gloats over how all Cole's work will soon be for nothing and how he should have returned home when he had the chance. However, Cole knocks Sedra down with an energy blast of his own before jumping on top of her and taking her life force.
In his room, Zedra is nearly done in downloading all the alien life forces from the cells - only for Cole to appear and quickly take Zedra's life force before narrowly aborting the download in time.
The next morning, Cole and Mel discuss all that happened - with Cole explaining how Cirronians 'get together' in comparison to how humans do it when Mel asks if there are similarities. Mel also gives Cole a present, with it been the 'kissing head' from the seminar. Both of them then agree that Cole cannot let his guard down again, although Mel thanks him for a 'wonderful weekend' before Cole returns to his work.
Tracker (TV Series) - Episode 14: Love, Cirronian Style
Tracker (TV Series) - Episode 22: Remember When