How to get every entity between two locations

Question

VMPlugin plugin = VMPlugin.getPlugin(VMPlugin.class);
Location target = p.getTargetBlock(null, 5).getLocation();
World world = target.getWorld();
Location ploc = p.getLocation();
Entity[] entities = //Entities between ploc and target (edit : straight line and everything up to 0.25 blocks away from it)

I tried Vector, but I don't know how to use it well.

Also if it is possible I would like to get only the first entity (If the EntityArray will work i will use just entities[0]).