Help him free

[Xinfu]

-Hercule Poirot helped John free.

Is it idiomatic and correct to use free to mean free of charge?

[Rusty]

Sounds odd to me.
I'd say "for free" or "free of charge."

[amyeme6414]

Interesting, my interpretation is that in this case, he helped him become free, as if John was somehow trapped or confined (likely physically but it could be more metaphorically as in an addiction) and Hercule Poirot helped set him free from the confinement.

[Xinfu]

Sounds odd to me.
I'd say "for free" or "free of charge."

Thank you.

[amyeme6414]

You're welcome, hope it helped!