Jogging board cargo

Club Penguin help plz answer? - how to get a black puffle without being amember for free

I am a secret agent on the PC, and I have a mission called Questions for a crab. I have to the part where the black Puffle followed me everywhere. My mission was to get the cancer, "G", but do not know how. The crab is in the cave and can not the door of the cave. How to solve this problem?