For all the soldiers there, Vietnam is already like hell. But one month after a US plane carrying a top-secret cargo codenamed "Whiteknight" is lost over the jungles of Cambodia, being in hell suddenly becomes even more appealing than being in Vietnam. After the plane crash, a Special Ops unit headed by Sergeant Caleb Walker is sent in to retrieve the cargo. In the end only Cal returns from this mission but he has changed. Something has driven him insane and unfortunately that thing has followed him out of the jungle.

Nate Walker, Cal's younger brother is now brought in to get information about "Whiteknight" from Cal who is kept in quarantine because he is carrying a highly contagious and horrifically destructive virus. But only moments after he meets his brother, VC forces attack the outpost and in the chaos Cal breaks out and escapes. Now it's Nate's job to hunt Cal down, solve the mystery of "Whiteknight" and survive the horrific nightmare called the Vietnam War.

The player puts on the boots of Nate and moves him in a traditional first person shooter fashion through the linear levels. These are cluttered with Vietcong and other more or less alive dangers. But grenades, pistols, M16s and other firearms as well as mounted machine guns help the player to hold his enemies at bay. If an enemy overwhelms Nate or in certain scripted situations, a quick time event starts in which the player needs to press the buttons shown on the screen as fast as possible or he'll meet his maker. If the player successfully survives the attack, they can then decide which way their opponent should die.

As with its predecessor Shellshock: Nam '67, Shellshock 2: Blood Trails doesn't hold itself back in terms of violence, gore and horrific imagery.