Here is your translation, adapted for natural American English while retaining the original meaning:
The story takes place in modern-day London, a city simmering with hidden dangers. The protagonist, Holt, is a down-and-out young man barely scraping by—until he unexpectedly discovers that he’s the illegitimate son of a powerful London crime boss. Suddenly, he's named the family's “number one heir.” Instead of bringing him wealth, this stroke of fate puts a target on his back as his two half-brothers go to extreme lengths to hunt him down.
Desperate to stay alive—and to buy time to raise £50,000 for his mother's life-saving surgery—Holt spends his last savings and, by sheer luck, hires a top-tier security expert, Henry, who’s hiding his true identity, at a “bargain” price. Thus begins an all-out battle between a novice employer and a deadly, seasoned bodyguard, as they fight back against seemingly impossible odds.
