It strikes me that many TV and movie plots these days keep on using the ability of snooping into someone's phone as a part of the narrative when so many modern smartphones have a fingerprint reader and wouldn't be easy to unlock, but what do I know? Maybe that's a necessary suspension of belief to keep the story moving. And you'll have to do the same while playing A Normal Lost Phone, but thankfully though, you won't have to pay a lot today to skip past the slightly shoddy premise and into the interesting game.
If the title wasn't enough explanation for you, the idea is simple: you found a lost phone and you have to rummage through the contacts, messages, calendar, email, browser history, and gallery, essentially snooping on every aspect of the owner's life, to piece the story together. The premise is ethically questionable, but it's a game after all and one that is very well rated (4.6 average with more than 1350 ratings), though some users complain about it being short.
A Normal Lost Phone is rather new, only having been released in January, and it usually costs $2.99. Today though, it's been discounted to $0.20 in the US or an equivalent amount around the world. This doesn't appear to be one of those geographically-limited deals so anyone can benefit from it.