March 5, 2015 2:36 AM EST

Sherlock Holmes will get a silver-screen twist when Sir Ian McKellen plays an elderly version of Britain’s most famous detective this coming summer.

Mr. Holmes, based on the novel A Slight Trick of the Mind by Mitch Cullin, follows a retired Sherlock as he tries overcome his failing memory to crack an unsolved mystery.

The trailer opens in the British countryside just after World War II and suggests the older Sherlock will rely not on Dr. Watson, but a young boy named Roger, played by Milo Parker, as his trusty sidekick.

The film is by Bill Condon, who recently shot the final two Twilight installments.

McKellen is a venerable Oscar-nominated English actor who has recently played Magneto in the X-Men movies and Gandalf in The Hobbit trilogy.

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