The state complement 个究竟
The state complement (状态补语) answers the question “how?” and describes an achieved state of an action.
Pay attention
A complement is a secondary part of a sentence. It is placed after a predicate expressed by a verb or adjective, and expresses the speaker's view of the chance of success.
The state complement 个究竟 
indicates that a person studies something in detail. In a sentence, it often follows the words like "to find out" and "to know".
indicates that a person studies something in detail. In a sentence, it often follows the words like "to find out" and "to know". Pay attention
In this case, the particle 得 is not used.
is not used.Examples
孩子们看什么都觉得新鲜，什么事都想知道个究竟
Children want to know everything because everything seems new to them
háizimen kàn shénme dōu juéde xīnxiān, shénme shì dōu xiǎng zhīdao ge jiùjìng
这事引起了我们很大兴趣，立即前往探个究竟
We were very interested in this incident, so we immediately went to find out what happened
zhè shì yǐnqǐ le wǒmen hěn dà xìngqù, lìjí qiánwǎng tàn ge jiūjìng
我听到很大的嗡嗡声，就起来想看个究竟
I heard a loud humming sound and got up to find out what was going on
wǒ tīngdào hěn dà de wēngwēng shēng, jiù qǐlái xiǎng kàn ge jiūjìng