We develop a two-layer asset demand framework to analyze fragility in the corporate bond market. Households allocate wealth to institutions, which allocate funds to specific assets. The framework generates tractable joint dynamics of flows and asset values, featuring amplification and contagion, by combining a flow-performance relationship for fund flows with a logit model of institutional asset demand. The framework can be estimated using micro-data on bond prices, investor holdings, and fund flows, allowing for rich parameter heterogeneity across assets and institutions. We match the model to the March 2020 turmoil and quantify the equilibrium effects of unconventional monetary and liquidity policies on asset prices and institutions.