When the Doctor tells Rose they're going somewhere specific, the TARDIS typically takes them elsewhere. Which is exactly what happens here. Except that they wind up in the middle of the Pacific front of World War II. In the middle of their honeymoon. And they begin to get shot at by the Allies off the shore. They run into the jungle, but two bullets hit Rose. Despite whatever the Doctor brags about, he's never been much of a medical man without his technology. He knows he has to get Rose back to the TARDIS, but he doesn't know how he will get past the gunfire. The Doctor has to face what losing Rose would really mean for him. And Rose, she has the fight of her life, with the man of her life by her side. Idea from @angelclonts