This is not straightforward. I've given some trailheads but you can start from other places too. Choose your path. I've also made this ridiculous story that is even less straightforward. And all of this came to my mind only because of the name of a track - O'Farrels Track. Cache is a peanut butter jar in a peanut butter jar.
Note: Although it is possible to access the cache via trails from Living Springs complex and the current management is informed about the cache, it is recommended that you make your assault from public access points, eg. Summit Rd.
Three geocachers, Cass, Ellas, and Faulkner, escape from a Summit Rd roadworks and set out to retrieve a supposed treasure Cass buried before the area is gone as it is a crater of a volcano that is about to come alive again. The three get a lift from a blind DoC ranger driving a lawn moving tractor. He tells them, among other prophecies, that they will find a fortune but not the one they seek. The trio make their way to Ohinetahi, a very reserved part of the land.
Ellas and Faulkner are baptized by a group of Christians at a Living Spring. The group then picks up Farrel, a young Maori man, who claims he has sold his soul to Rūaumoko in exchange for the ability to play the guitar. In need of money, the four stop at a radar broadcast dome where they record a song as The Slopey Hills Boys. That night, the trio part ways with Farrel after their tracks are discovered by the local walking club. Unbeknownst to them, the recording becomes a major hit.
The next day, the group hears singing. They see three women washing clothes in a spring and singing. The women drug them with flax seeds and they lose consciousness. Upon waking, Faulkner finds Ellas' clothes lying next to him, empty except for a pill container with a strange note inside. Faulkner is convinced the women were Smelly Toes and transformed Ellas into the pill container.
Cass and Faulkner arrive in Cass's home town. Cass confronts his wife Bellbird, who changed her last name and told his daughters he was dead. He gets into a fight with Mr. Rim Crater, her new "suitor." They later see Ellas working on a chain gang. Later that night, they sneak into Ellas' holding cell and free him. As it turns out, Smelly Toes had dragged Ellas away and turned him in to the park rangers. Under torture, Ellas gave away the treasure's location to the walking club. Cass then confesses that there is no treasure. He made it up to convince the guys to help him with bush-bashing.
The trio stumble upon a rally of angry farmers, who are planning to hang Farrel. The trio disguise themselves as farmers and attempt to rescue Farrel. Chaos ensues, and the trio rush Farrel away and leave all the farm gates unchained.
Cass convinces Ellas, Faulkner and Farrel to help him win his wife back. They sneak into a muggle picnic she is attending, disguised as musicians. The group begins a performance of their radio hit. The muggles recognize the song and go wild. The Chief ranger endorses the Slopey Hills Boys and grants them full access to Ohinetahi. Bellbird agrees to marry Cass with the condition that he finds her original ring.
The next morning, the group sets out to retrieve the ring, which is in a geocache in the valley which Cass had earlier claimed was the location of his treasure. The walking club, having learned of the place from Ellas, set out to find the cache first. Just as Cass prays to God that they don't take the ring, the volcano erupts and delays the walking club. Farrel finds the geocache, that was high enough not to be sumberged in the lava, and they return to Summit Rd. However, when Cass presents the ring to Bellbird, it turns out it was not her ring, she doesn't want that one, and she can't remember which cache she put the real ring in.
This story was loosely based on the plot of O Brother, Where Art Thou?