YA Spy(ish) book with Plot twist opener, about an ordinary guy doing favours for a mystery evil organisation, on the last one he gets suprised killed by the bomb he is planting.

I remeber reading a Young Adult book in my teen (15 years ago?). I think it may have been an Alex rider (by Anthony Horrowitz) or Artemis Fowl (Eoin Colfer) book, or something of a similar genre (teen fights big evil organisation etc). Im seem to remeber it being one of the later of a series, but I could be wrong.

In the introduction, we meet a new ordinary man (I think something along the lines of hes a janitor or imigrant worker), completely unrelated to anyone before in the books, who is currently completing his *third* job for a slight shady and mysetrious someone, we dont know who (mob, organisation etc). He reflects upon how in the previous task the people have paid him well (something like he picks up a suitcase, and they pay him $100. next job he does they mail him an ipod or playstation as a reward) In this job, there offereing a big reward ($100,000k), and all he has to do is plant a bomb in a duffle bag somewhere, and walk away.

He plants the bomb in the spot hes instructed, and presses the button to arm it, but instead of the timer showing 5:00 min like they said it would, >!it only shows 5seconds, and he dies along with the explosion !<

Its basically a big mystery plot twist as to who these guys are, next chapter were introduced to our main character, they fight, teen hero wins etc.

I cant remeber what the exact early tasks were, how many there were, and rewards might not be acurate, but it was definelty large rewards for very simple tasks early to sucker him in, and then the promise of a big reward for this bomb planting task, but it never happens, casue the guy gets suprise killed from the bomb exploding early.

I really want to find it again, as its a great analogy for suckering people into scams with behavioural rewards, and large promises.