In viewing Rash"i on Bemidbar 13:21-22, it seems that the Torah lists things out of order unless it is describing "general" first and then "specifics".
In other words - in reading Rash"i on verse 21, he says that they started in the southeast corner of the land, and returned going south along the western border by the sea (Mediterranean).
Verse 22 says "They went up the Negev and he came to Chevron."
Since Moshe said "Go up the Negev and climb the mountain," (verse 17) I'm inferring that this is how the spies started their travels. If I infer correctly, it seems that at some point while travelling north, Calev separated (see Rash"i on verse 22) separated from the rest of the group, and he went to Chevron.
OK - then what? Did he rejoin them? Did the rest of them continue travelling northward and eventually Calev caught up, or did they wait for him to return from Chevron? And, in general, do we know if all the other tribe leaders stayed together during the whole mission, or did they split up (besides Calev) along the way, and then rejoined somewhere else?