The 5th episode of The Flash airs today, Tuesday, 11th November at 8 pm ET on The CW.
The episode is titled, Plastique, where Kelly Frye and Clancy Brown guest star as DC Comics' Plastique and General Eiling respectively.
Click here to watch the episode online.
The official synopsis reads:
The much awaited mash-up will happen in The Flash's 8th episode, which will air on 2nd December, and is titled 'Flash vs Arrow'
Arrow's Executive Producer Andrew Kreisberg told TV Guide that fans should catch up on all The Flash episodes to be ready for the crossover special.
Kreisberg said that episode 8 of The Flash will be an important one for both series.
He said: "We discover something about Oliver (Stephen Amell) which is probably one of the biggest secrets we've ever revealed on the show — and it happens on 'The Flash'."