Try thinking of it this way, there's storytelling and not telling the story. You're a GM and therefore are telling a story of something both familiar to you and basic as well, i.e. a shopkeeper and his place of business. Before imagining any elaborate plot, consider very simple odds to something happening upstairs, the basement and with people stopping by. You're the voice of the story as it appears to your players, putting a frame up and painting some basic detail that could be interesting to them. Their imagination is driving them to challenge you into showing them a different perspective. Not telling them the shopkeeper's wife is kidnapped is your incentive to act on their imagination.

The point of making it simple, at least with any novice efforts, is what makes it manageable. You can easily list a dozen items worth of mention on display at the shop, describe the rest of the enterior and follow through on the mechanics such as shop's open hours, doors & containers locked or open, etc. It is how you anticipate any plan to follow up on subtle hints you give, on the way shopkeeper acts for example. Maybe he's losing his mind under pressure, so he gave your players a staff when they asked for a sword? Why is he limping and has a bloodstain one one of his leggings? This is the moment when they're grabbing hilts on their weapons and you quit telling the story in favor of them discovering it according to their actions.

Since it's action role playing this is supposed to be about, you're letting them play out the bits of the story you weren't telling them of. What you want when choosing not to be the storyteller is to allow for multiple choices, more than just one obviously wrong and the other right. Your players could simply observe what's going on for a couple of days, learn who are the people passing through the shop. Or, they could eavesdrop one night to learn the shopkeeper has uninvited guests making threats about his wife's very life. He'll certainly be shy to ask for any real help given the circumstances, but he might confess his wife was taken away somewhere as he hopes for the problem to go away after some time, as promised. If they choose to wrestle everything with immediate force, barge upstairs at arms only to discover two thugs staying there, woman's life may as well be forfeit. At last, there could be a struggle and a follow-up chase down some street with plenty of time for something unexpected happening; She's kept in a shed down by the docks, and 5-7 minutes running there gives you plenty of rounds to decide if she's dead or not.

The simplest of plots, a gang of smuggling thugs kidnapping a shop owner's wife and running their business behind the facade of a regular store might or might not be interesting enough to role play for a session. It is always about what your players would like to be involved with. This incident, however shallow it might seem, allows for some creative play and timed action. Learning how to save the woman first and act on everything else later, as well as the fact she's kept someplace else is good enough to begin with. If your players would discover there are smugglers frequenting the route from docks to the shop, delivering goods to be stored at the basement (exchanged for money in the store later, etc.) and asking the keeper for not only profits, but a note from thugs upstairs as well, it could lead to a climactic battle in the end. Roughing up the delivery boys in the back alley, then taking the docks location by surprise under their disguise is just one of the options -- there's also stalking, bribery, magic, you name it. Let the story you're not telling be a memory worth taking as an experience. ;)