  Inchargeness is associated with one's authority in driving the activity in
collaboration. We study how inchargeness changes within a collaborative group
when its members have differing expertise. We present a case study of a group
of three students working in an upper division undergraduate physics
laboratory. One of them has less on-task expertise than her peers due to
missing a day, which reduces her relative inchargeness across two storylines:
"catching up" and "moving forward".
