The first Boniface knows about the dead body in the next room is when he is arrested for murder.
The lack of evidence against Boniface doesn't seem to concern the police--they are sure they have the right man--they just need to prove his guilt, and while they do, Boniface is bailed allowing him to return to work with his client.
His client, a shipping company, couldn't care less that Boniface is distracted. The client has its own problems: News is about to break that one of its ships dumped toxic waste in East Africa, leading to painful and lingering deaths, as well as widespread disability and illness. While the company privately acknowledges its role in the dumping--and its ongoing responsibility for the welfare of the victims--it is insistent that Boniface keeps the story out of the public domain until it has fully assessed how it can most effectively deliver support to those affected.
Boniface knows he has been set up for the murder--and that somebody is trying to destroy him, his business, and everything he holds dear--but he doesn't know who has set him up, or why. He strips back the layers, discovering who the dead man was, why he was killed, why the body was dumped in his office, and why he was set up in such a clumsy manner until, he finds who has endangered his livelihood, his liberty, and his friends.
This leaves Boniface with only one conclusion: He must neutralize the threat, permanently, while at the same time trying to protect anyone affected by the dumping.