What does "仲間達の手によってM事件はすっかりカタがついていた" mean?
I am struggling with the sentence because I don't understand the function of "手によって", "すっかりカタが", or "ついていた".

I appreciate any help or insight :)

Question

What does "仲間達の手によってM事件はすっかりカタがついていた" mean?
I am struggling with the sentence because I don't understand the function of "手によって", "すっかりカタが",  or "ついていた".

I appreciate any help or insight :)

Answer

手によって　ー＞  by (their) hands ＝＞ thanks to their effort
(すっかり) カタがつく　ー＞　to come to an end ＝＞ a problem is  completely  solved
すっかり　＝＞ all, thoroughly, entirely