What shall we have our characters capture? Why do they need to capture it?
A magic unicorn? Why? Why do they desperately need a wish granted?
A wild stallion? What will it help them accomplish?
A dove? A rabbit? A deer? What do they need these for?
The dove could carry a message. Rabbits and deer usually end up as campsite food in stories. Maybe the deer is a caribou. Would we have our hero train it like a pack animal or ride it like a pony?
Capture the runaway steers, the escaped convict, the lost lambs. Capture important papers before they are carried away by a roguish wind. Capture the runaway hot air balloon with a helpless person in its basket. Capture the fleeting heart of a doubting person who can't seem to find his or her way back home. Capture the model boat whose string snapped, leaving its owner tear stained on the river bank. Capture the raft before it reaches a waterfall. Capture a fish for a pet or for your dinner. Above all capture the readers while you set about obtaining whatever else your characters are after. Make their minds want to stay with your story or your series.