AVENGERS: Age of Ultron, the latest instalment in the Marvel Comics franchise, is set to be spring's mammoth blockbuster.

Not sure who's who? Let us introduce you...

It's been three years since Iron Man, Thor, The Hulk, Captain America, Hawkeye and the Black Widow, banded together in The Avengers. Now the sequel's almost upon us, and it's set to be even bigger and better than their last outing.

Once again, S.H.I.E.L.D. - the international peacekeeping agency made up of Marvel Superheroes, must use their powers to save the world from catastrophe. This time, there's a new enemy, Ultron, a programmed robot (voiced by James Spader), with a mission to destroy humanity.

Missed out on their first adventure? Let us bring you up to speed...

:: Robert Downey Jnr. is Iron Man

Iron Man's brought to life by billionaire playboy genius Tony Stark, who's created an electromechanical suit that transforms him into a human robot. When we meet up with him, Stark, the Avengers' co-leader and benefactor, is still feeling guilty from the fallout of the 'Battle of New York' in the last film. In an effort to restore peace, he tries to jump-start a dormant peacekeeping programme with the help of Dr Bruce Banner, aka The Hulk. Only, things go awry, and the Avengers must assemble once again, to stop Ultron before it destroys mankind.

:: Chris Evans is Captain America

Steve Rogers was too sickly to fight in World War II but, after agreeing to play guinea pig, was physically enhanced by an experimental serum, to become the super-soldier known as Captain America. Frozen for decades, he awoke to find himself in the modern era and continues to try and come to terms with living in a world he doesn't fully recognise. When Ultron presents himself as a new threat to humanity, Captain America, as Avengers' co-leader, is the one who rallies the team to prepare for battle.

:: James Spader is Ultron

Although created by Tony Stark, aka Iron Man, and Dr Bruce Banner, aka The Hulk, to ensure peace on Earth, Ultron's programming goes haywire, resulting in the robot thinking it's mission is to wipe out all of humanity. With the ability to access anything technological, including the entire internet, it's a formidable force.

:: Scarlett Johansson is Black Widow

The super-spy of the team, Natasha Romanoff, aka Black Widow, doesn't have any 'super' powers as such, but her intelligence and lethal fighting ability ensure she can more than keep up with the boys. Her smart thinking will be needed to fight off Ultron and save the world from peril. Producer Kevin Feige says we can expect to see more of Black Widow's backstory explored in the sequel.

:: Mark Ruffalo is The Hulk

The Hulk was born when genius scientist Dr Bruce Banner, who aids Stark with the Ultron programme, was exposed to radiation that turns him into a green monster whenever angry. Keen to keep The Hulk in check, Banner's brought in new protocols, such as listening to calming classical music. But will it prove enough? Suffering from an identity crisis, it's Natasha who looks like she might be able to help him fight his demons.

:: Chris Hemsworth is Thor

The hammer-wielding god Thor continues his work with the Avengers in order to protect the human race. He warns the other Avengers of threats and acts as their moral compass, questioning the team's actions.

:: Jeremy Renner is Hawkeye

After having his mind controlled by supervillain Loki in The Avengers, Hawkeye now has full control of his thoughts. Renner, speaking of his character, says that we will get to see why he thinks the way he does in the sequel. A superhuman archer, with the ability to fire augmented arrows with precision, Hawkeye will prove to be a vital part of the team when they go up against Ultron.

:: Samuel L. Jackson is Nick Fury

Fury is the director of S.H.I.E.L.D and the mastermind who initially recruited the different superheroes to create the Avengers. A great strategist and mentor, Fury must once again bring the Avengers together to defeat their latest enemy.

:: Elizabeth Olsen and Aaron Taylor-Johnson are twins the Scarlet Witch and Quicksilver

Making her debut in the film franchise is Elizabeth Olsen, who plays the beautiful and cunning Scarlet Witch. Her superpowers include telekinesis and hypnosis. Teaming up with her is Nowhere Boy's Aaron Taylor-Johnson as her twin brother Quicksilver, who's faster than the speed of light - when he wants to be. They want to stop the Avengers, believing they are bringing destruction to the world, but will they change their minds when they get to know the team?

:: Avengers: Age of Ultron opens on Thursday, April 23