Irina can be found in this stage by breaking a wall on the left side of the waterfall room. The waterfall must be unfrozen first, however, by absorbing the Vol Grandoglyph located at the top.
Tom can also be found in this stage once Irina has returned to Wygol Village and Anna gives her first quest. He can be located perching atop one of the tallest trees at the third room of Tristis (entering from the left).
The second quest for Daniela's Sketch Book item can still be completed even if the waterfall is still frozen.