When exploring the beach I stumble on a rusty knife. But none of us brought a knife like this.

It's centuries old, and the design is medieval. It must have belonged to Arne Saknussemm! He was here!! He must have dropped it and run - but from what? Or could some other early explorer have reached here?

Should I look for more evidence on the ground? Or is the secret in a nearby blocked cave? Or should I do something else?