The theory of karma is NOT based on stupid concepts just because we mortals are unable to fully grasp them.
What sort of trouble? Please be specific so that I can explain to you how karma works, given my limited knowledge of the subject.
The converse is also true.
An example: a person such as LKY became the de facto Emperor of a TINY city-state because of his previous good karmas. Instead of accumulating more good karma while he was Emperor, he decimated it by persecuting good people, heaping false and malicious accusations against his real and PERCEIVED rivals, throwing them into jail, permitting and promoting cronyism and nepotism, etc....
In the end what happened to him after his demise? The once highly exalted Emperor of a tiny country has now reincarnated in a poor village somewhere in India. He's now born to a low-caste Hindu family. His life ahead won't be as rosy as the one before him. That's karma at work.
You have to be more specific about what sort of trouble the person(s) is/are in.
Generally speaking, if a person is in trouble--however big or small--it could be due to his previous bad karma. Sure, you aren't obliged to help him, YOUR (not my) reason being that you don't wish to interfere karma at work.
But if you DO help him to get out of trouble, YOU will be accumulating good karma for your next life (unless you decide to attain nirvana). Karma allows and even encourages do-gooders such as yourself to help those in trouble (who got into trouble because of their previous bad karma).
One concept in the theory of karma is that it has a multiplier effect that isn't limited by the space-time continuum (a/k/a dimension).