The answer is: In a dream

Matt 2:13 - The angel only appeared to Joseph in a dream and didn't actually visit them in a physical sense. Also the angel appeared only to Joseph and not to them both.

In the drama of Jesus' early life, dreams play a surprisingly crucial role. This moment from Matthew 2:13 is actually one of several instances where divine messages come through dreams. It’s interesting to note that in the ancient world, dreams were often seen as vessels of revelation, connecting the mortal realm with the divine.

Joseph's dream tells us much about the importance of his role in the narrative. He’s portrayed not as a side character, but as an integral part of God’s broader plan. Unlike in secular tales where a mere man might be swept aside, Joseph stands firm, accepting direction in a precarious situation. It echoes themes found throughout the Bible, such as those seen in the dreams of Jacob and Joseph of the Old Testament, hinting at a divine purpose unfolding across generations.

The accommodation for fledgling parenthood even leaps to the New Testament in something more modern: think of how parents today view signals in their children lives. Instead of relying on angels, they often look for signs, advice, or their own instincts. In Joseph's case, his ability to act differentiate him as a protector, a massive responsibility resting on his shoulders.

Moreover, it’s worth noting that there is another escape from danger: the use of Egypt as a refuge. Egypt was fundamental in both oppression and refuge within biblical narratives, from the Israelites fleeing to Egypt during famine to establishing conventions across influential Jewish communities. Joseph's flight reflects this layered symbolism, making their journey a rich thread within the tapestry of biblical history.