L.E. Fitzpatrick 
Border Lines [EPUB ebook] 

When the perfect job comes up, Charlie doesn’t have to think twice.
This is the break he’s been looking for, and nobody – not even the rest of his team – can persuade him otherwise. The job means working for an old enemy and crossing the border into London.
Both are risky, but Charlie has no idea how high the stakes really are. The team will have to confront their past, each other and a killer who is closer than they realize.
But can they make it out of the city alive?