Video story question answering (video story QA) is a challenging problem, as it requires a joint understanding of diverse data sources (i.e., video, subtitle, question, and answer choices). Existing approaches for video story QA have several common defects: (1) single temporal scale; (2) static and rough multimodal interaction; and (3) insufficient (or shallow) exploitation of both question and answer choices. In this paper, we propose a novel framework named Dual Hierarchical Temporal Convolutional Network (DHTCN) to address the aforementioned defects together. The proposed DHTCN explores multiple temporal scales by building hierarchical temporal convolutional network. In each temporal convolutional layer, two key components, namely AttLSTM and QA-Aware Dynamic Normalization, are introduced to capture the temporal dependency and the multimodal interaction in a dynamic and fine-grained manner. To enable sufficient exploitation of both question and answer choices, we increase the depth of QA pairs with a stack of nonlinear layers, and exploit QA pairs in each layer of the network. Extensive experiments are conducted on two widely used datasets: TVQA and MovieQA, demonstrating the effectiveness of DHTCN. Our model obtains state-of-the-art results on the both datasets.