Comic book shoppers in Australia could only marvel as Spider-Man swooped to prevent an in-store robbery.

The hero inside the suit was Adelaide Comic Center owner Michael Baulderstone, who was dressed up to celebrate International Free Comic Day.

But justice was called for when one man took the offer of a free read a little too literally and attempted to lift an X-Men Omnibus worth over $150.

As a packed crowd including Jedi Knights and the Flash stood by, Mr Baulderstone showed his 'spider-sense' to step in.

The 45-year-old spotted the man "behaving suspiciously" at the back of the shop and challenged him to hand over his bag.

Surrounded by a network of around 40 super heroes, the would-be thief surrendered, revealing the valuable comic.

Click here for more on this story from SkyNews.com.