Her Story is the story of Hannah Smith - a woman who is being interviewed by the police after her husband is found dead.

Now, a decade-or-so later, you're trying to piece together the truth by hunting through short video clips, all catalogued on some crime-fighting computer program called LOGIC that tags interview clips by words spoken in the video.

So, if you type in "Murder", you'll get a handful of videos where Hannah says "murder".

From there, you'll watch clips and hear names (like Simon) and places (like Glasgow) and things (like a mirror), which give you new words to search for, and - hopefully - new clips to watch.

Bringing up the bodies

You'll see Hannah - played marvelously by actress Viva Seifert - answer some questions, evade others, and give off different vibes in different interviews. Naturally, you'll have to decide whether you completely trust her testimony.

Then you get a hunch. Maybe Hannah's not telling the truth about something. Or you think you know something the police don't. You key in your phrase, and hit the button.

The computer hard drive whirs to life, a progress bar creeps along, and suddenly new video clips appear. Clips that confirm your suspicions, validate your hunch, and send you spiraling down some new avenue of inquest.

It is an incredibly satisfying experience. You feel like a detective who's just cracked the case. It's True Detective meets Serial meets searching on Google.

Soon, you'll grab a pen and paper in real life and start jotting down things you learn. You'll establish a timeline of events, a database of people, and a list of potential search terms. And you'll get dragged deeper into the story.

Cold case

Credit of course must go to creator Sam Barlow, who has masterminded an experience that is both extremely open ended (as you can search any word you like) but also skillfully directed.

You might think you're acting independently, but clever design and even sharper writing pull you down certain directions like you're on a leash.

Her Story is as engrossing as a good novel. I'd call it unputdownable, like they say on the back of schlocky books, if I didn't hate that word. But it holds true - I played the entire game in one, long, utterly mesmerising sitting.

The story is gripping and unpredictable. Some clips make Hannah seem grief stricken about her husband's death, while others make her seem callous and uncaring. Stories contradict each other. And surprises drop often.

Secret in her eyes

It can also be a moving experience. And Seifert does tremendous work creating a rich character who is equal parts mysterious, empathetic, and suspicious.

I wish it gave a few more opportunities to make you feel smart. Because those fleeting moments when you type in some unmentioned phrase, on a hunch, and get clips that send you off on a completely new branch in your investigation, are magical.

Her Story is one of the most entrancing experiences you can hope to find on mobile.

Her Story will be out on iPad and iPhone on Wednesday