Answer:
In this ELISA procedure, a sample of protein is immobilized in the plastic well and then antibody for this protein added and incubated, and cleared out. In the given setting detection, the antibody is conjugated with the protein of interest and if the substrate molecule added to the reaction it will produce a colored product by reacting with the enzyme.
No reaction will take place in the well in case of not adding secondary antibody or detection antibody to the reaction and no colored product will be received.