How to overwrite a controller method for one module from another

[john_dou]

Hello!
I have one subscription module on Prestashop 1.5. I need to put the recaptcha on the form (I did this) and redefine the subscription module controller on my own (substituting my part of the code there), and then continue the subscription controller.
I tried to redefine the file to the subscription module in the path (modules / my_module / override / modules / subscription_module / controller / front / subscription.php), tried to add the file along the path (override / modules / subscription_module / controller / front / subscription.php), but the controller does not want to be replaced.

class SubscriptionModuleFrontControllerOverride extends SubscriptionModuleFrontController{
public function postProcess(){}

Please tell me how to correctly override the module controller method and continue its execution?