The Time Afterwards

Arendelle is at peace again. Anna and Elsa have formed an incredible bond. Anna and Kristoff have..... Stronger feelings than before. Olaf still loves warm hugs. Sven still loves carrots. Prince Hans is still an enemy. All seems to be normal; until someone shows up in Arendelle and causes the Southern Isles and Arendelle to go into war. Can this certain someone help Anna and Elsa stop the war? Or will the war only march on?