Set after Miracle Day also spoilers for Children of the Earth.
Ianto woke up in thing he remembered was dying in Jack's arms. He wondered if he was immortal now. He tried to leave UNIT but it didn't take them long to figure out that Ianto was back to life and capture him and run tests on him.
When Ianto finally escaped he wanted to go see his family but didn't fearing that that would put them in danger. Then he tried to find Jack only to find out from Gwen and Rhys that Jack had left Earth because he thought that Ianto was dead and he didn't find the irony in that the least bit funny.
I hope I find you one day Jack,Ianto thought as he looked up at the night. He knew that Jack could be anywhere other than Earth and he wondered how long he had to find his Captain.