Finally, after a one week hiatus, "Arrow" season 4 is back and fans should expect the episodes this week from both CW series to be action-packed.

It is time for the cross-over wpisodes of "The Flash" and "Arrow" as they face perhaps the strongest villain they've faced so far, Vandal Savage who is an immortal. It will take the combined effort of both Team Flash and Arrow to take him down but the question is, will they be able to?

With that said, here's the synopsis of "Arrow" season 4 episode 8 via "Arrow" wikia. This episode will be the part 2 of their encounter with Savage.

"Oliver and Barry Allen take Kendra Saunders and Carter Hall to a remote location to keep them hidden from Vandal Savage while they figure out how to defeat him. Malcolm arranges a meeting between Vandal, Green Arrow and The Flash that doesn't go as planned. Meanwhile, Felicity, Thea, Diggle and Laurel work with Team Flash to come up with a weapon powerful enough to destroy Vandal Savage." 

The episode after that, Oliver will make another move against HIVE but it looks like Damien Dahrk will get the better of him in that episode. Here's the synopsis for "Arrow" season 4 episode 9 via Comic Book Movie.

"OLIVER TAKES ON HIVE - After the city is attacked again, Oliver (Stephen Amell) makes a bold move against HIVE.  Malcolm (John Barrowman) checks in on Thea (Willa Holland) and leaves  her  with a  warning." 

"Things  take  a  horrible  turn  when Damien Darhk (guest  star  Neal McDonough) retaliates in a brutal manner at Oliver's mayoral holiday party.  John Behring directed the episode written by Wendy Mericle & Ben Sokolowski."