If the interaction effect in the two way ANOVA is significant (based on a sig level = 0.05) and none of my main effects are significant, what can I infer from this?

I suppose I am not understanding the overall picture of the two way ANOVA. You test the significance of your mean response over two main effects and then you test whether there is an interaction between your independent variables. Surely I cannot assess the main effects in isolation of the interaction effect and vice versa?