The Flash | 8pm | The CW

When a powerful alien threat arrives on Earth under mysterious circumstances, Barry (Grant Gustin), Iris (Candice Patton) and the rest of Team Flash are pushed to their limits in a desperate battle to save the world. But with time running out and the fate of humanity at stake, Flash and his companions will also need to enlist the help of some old friends if the forces of good are to prevail.