"Limitless" Season 1 is going in full swing with a lot of things happening around. And over the last 5 episodes we have seen Brian Finch only giving/ living up to Senator Morra's demands to get his regular supply of NZT drug. It looks like Brian's struggle continues in episode 6, titled "Side Effects May Include..."

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In last week's Episode 5 we saw Brian struggling hard to keep secrets revolving around NZT, his life and Rebecca's late father. "Personality Crisis" saw how Brian figured that working with FBI wasn't all that fun. While he was seen struggling through the idea of telling Rebecca about her father and NZT, but his NZT version was adamant to do so. But at the end of the episode, Brian handed Rebecca some files, and it looks like it could be documents about NZT that he stole from Naz.

So, if we go by the theory that Finch has told Rebecca about NZT, then we have to see if he will actually betray Rebecca as per Senator Morra's wishes. The NZT drug has started showing its side effects and Brian badly needs another shot of the vaccine as his health is deteriorating without it.

The promo of this week's Episode 6 clearly shows Bradley Copper making a comeback for another cameo as Senator Morra and demanding Brian to deceive his FBI colleague Rebecca, in exchange for another inoculation that prevents him.

Meanwhile, the preview of "Side Effects May Include..." also teases that Brian has secretly started looking for an alternate cure for himself while he works with Rebecca outside FBI parameters to find the creators of NZT.

Plot synopsis of "Side Effects May Include..." reads: [via TV Guide]

"Brian's physical and mental health begin to deteriorate again, but Edward Morra is demanding a high price in exchange for another inoculation."

"Limitless" Episode 6 titled "Side Effects May Include..." will be aired on CBS on 27 October, 10pm.