Post History
Give the victim a reason to betray the good guys. Make the victim a rounded character. Give him or her motivation, backstory, and personality. The reader may not see all the backstory you've creat...
Answer
#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/18929 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/18929 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
Give the victim a _reason_ to betray the good guys. Make the victim a rounded character. Give him or her motivation, backstory, and personality. The reader may not see all the backstory you've created, but you as the author should know what it is, and write the person accordingly. Maybe the victim is being blackmailed by the bad guy and is genuinely sorry to trap the good guys. Maybe the victim is the bad guy's secret sibling/spouse/servant/child. Maybe the victim owes the bad guy something, and trapping the good guys is just business, nothing personal — it's a favor to the bad guy. Whatever the victim's reason, remember: Each of us is the hero of our own story. Consider from the victim's perspective why s/he would do such a thing, and why s/he would want to hide his/her motivations from the good guys. That's how you can set up the surprise.