The clues are four 4 digit numbers. This Wherigo cartridge will give you some information to enable you to discover where these clues are. The cartridge can be started anywhere - you can even start it at home - but you will need to travel to 5 or 6 different locations to obtain all the information you need. You are able to choose the locations to visit 
. The only advice we can offer is that the greater the distance you travel between your chosen locations the more successful you are likely to be.
In order to ensure a reasonable chance of success we recommend that you maintain a distance of at least 10 kilometers between your chosen locations. The cartridge will measure an approximate distance based on compass points and unless there is at least 7 kilometers in any compass point direction from your previous location the cartridge will not reveal any further information to you. The cartridge instructions are only presented once on start up; read them carefully so that you understand how the cartridge works and what is expected of you.
Before you start please note that because of the potential distances you will need to travel to solve this puzzle it has been designed so that you can complete it at your leisure over a period of time; we don't want to impose unnecessary travelling on fellow geocachers. So we recommend that the information is collected as and when you can obtain it as you travel around doing other things, rather than embarking on a specific expedition to solve the puzzle all at one go (it spreads the enjoyment as well
). FTF enthusiasts will obviously ignore this advice. You must remember to save the cartridge each time you close it and then choose the "Load saved game" when you restart it or you will need to start again from the beginning.
Our whereigo file is on the wherigo website Wherigo.com. When you have the software needed download this file:- The Rhubarb Triangle. Good luck!!
Once you have the required four numbers arrange them in a 4x4 grid with Clue 1 as row one Clue 2 as row 2 etc. If you then reference the cells A,B,C etc left to right and down the rows; the cache can be found very close to:-
N BH EA.PKN W CCP AO.HNM. Take a picnic!! 
If this puts you inside "The Rhubarb Triangle" then you can be almost certain you have been successful. The sum of all 16 digits in the grid should be 66. You will need to have the Wherigo active at GZ to get your Completion Code and be given some some final simple directions. First, second and third to find will have some geocoin prizes to take away, see photos.
If you don't know where The Rhubarb Triangle is or why it is important (shame on you!!) this link will help educate you. Map of the Week: The Rhubarb Triangle.