MongoDB failover process
So assuming that node(n) is a physical box, and the host(n) is a mongod process...If the link between the nodes fails, nothing cool will happen :).

node1 will continue operating as normal, and node2 will just sit there asking wtf.  The regular secondary will only have 2/4 votes which is not the strict majority.

If node1 fails, then you will have to manually configure the secondary on node2 as the primary.

When node1 comes back online, the previous primary will come back online as a secondary and it will detect any unfinished writes, and do a rollback which will require manual intervention.

Keeping in mind that you need a strict majority to elect a new primary, I would try putting the arbiters on their own system that is independent of the two nodes.