Michael R. Stern 
Storm Unleashed [EPUB ebook] 

As the president negotiates to end war in the Middle East, another plot to destroy peace moves into high gear.
Meanwhile, Fritz returns from a trip through the portal, and realizes that the world around him has changed. After the White House comes under attack, Fritz is once again called to action.
The portal is a powerful tool, but entering it risks undeniable danger. It’s their only way to stop the enemy. But at what cost?