Midway through Chapter 1, you will follow Achaka down The Well you were previously in (with The Dragon). As this "story" takes place earlier in time, The Well will have different paths for you to follow.
After 2-3 screens at the start of The Well, you will enter a screen where Achaka slides down a rope and motions to you not to follow. Instead of going down the rope yourself, continue heading towards the right side of the screen.
From here you will follow a linear path until you hit a dead end overlooking a large section of The Cave. From here, just hang around or walk in circles while Old Graham and Gwendolyn chat about what Young Graham is doing. Eventually Gwendolyn will convince Old Graham that he did a dance and thus, Young Graham will comply.
After the dance the screen fades and finds a Young Graham back at the rope ready to slide down to Achaka. The trophy should then pop.