Our concepts of a God active in the world are challenged by the appalling and exhilarating history of the 20th century. It is quite obvious that the crude mechanical explanations of biblical times do not stand up. There has to be a much more subtle explanation. For my part, the only conclusion I can reach is that God has given the whole Creation, and especially us human beings, the freedom to develop the potential it has.
However this does not mean that God has simply 'lit the blue touch paper and retired'! At the right time in our human history God has come in Christ and poured out his Holy Spirit. This means that we have the necessary help available to us.
When we take note of this help in Christ and the Holy Spirit then God is there for us. We are enabled, like the Ninevites to repent and go in God's new direction.

Sing praise to God, his mighty name extol,
Great is the Lord and worthy of our praise.
Our God deserves our blessings and our love,
Our duty is to serve God all our days.

When we think about our God's mighty deeds
We have a glorious message to proclaim.
The whole Creation to enable us;
And God's own Son to be our Saviour came.

To know these things enlarges all our mind;
God's Holy Spirit gives us all his light.
God is compassionate to help us here,
That through his Son we each may live aright.

Christ gives life;
For he is the one who has saved us.
Christ gives life;
This the gospel word.
Here today we witness together
Jesus Christ alone is sovereign Lord.

Christ gives hope;
Since he has been raised up for us.
Christ gives hope;
He awaits us there.
In this life we travel together'
Jesus journeys always with us here.

Speak the word;
Your witness to Christ is important.
Speak the word;
Christ is your saviour.
Play your part, that all may hear of him,
His example sets our behaviour.

This story tells of the inherent openness of God's dealings with us. It also tells of the astonishing, and utterly unmerited, generosity of God. From this it becomes obvious that our worldly concepts of 'fairness' simply do not apply in the matter of salvation.
God's act, by coming in Jesus, offers us a pattern for a higher quality of life than we can otherwise achieve. Jesus' act, by dying for us on the cross, offers us freedom from the burden of sin. God's act, in raising Jesus to life eternal, gives us hope beyond the temporal limitations of our earthly existence.
Whilst it is, obviously, much more desirable to 'come to God' early in life. This story shows us that our reward, of salvation, is the same whenever we come. It is, as Charles Wesley put it "unmerited and free".

We are workers in God's vineyard,
Each one has a job to do.
Soon or late, it doesn't matter,
He will call, by name, to you.